Abdul Yamuremye almost left it too late. For months, friends and neighbours had been packing up and fleeing, driven from their homes as the attacks by the men with the guns and the machetes became more brutal and more random.

Yamuremye had spent years building a successful scrap metal business in Burundi's capital, Bujumbura. He knew that when people ran before when political crisis in the country turned to bloodshed, all their assets and land were looted. He was determined to do all he could to avoid that.

But then, the Thursday before Easter, the men with the guns and machetes arrived at his door and it became clear it was time for him to run, too. Within minutes, his two teenage brothers, a friend who lived with them, and her son and two daughters including one still a toddler were dead. His house, he said, was 'painted in blood'.

It is a year since Burundi's political crisis erupted, sparked by President Pierre Nkurunziza's decision to run for election again despite already having served his constitutionally-mandated two terms in office.

His move sparked street protests then deadly security crackdowns. More than 3,400 people have been detained and more than 400 have died, the UN estimates. It is a common story in the young democracies of Central Africa: Rwanda, the Democratic Republic of the Congo, the Republic of Congo, and Uganda all have leaders in place who have already over-run their tenure, or are set to.

What is not so common is what happened in Burundi once the world's attention moved on from the initial clashes a year ago. In the first surge of violence, the ruling party unleashed its thuggish youth wing, the Imbonerakure, whose armed members swept the country hunting opponents.

That wave of terror spawned reprisal vigilante gangs opposed to the president, who retaliated. Amid the chaos, opportunistic criminals seized their chances. Burundi's demography of Hutu and Tutsi tribes matches neighbouring Rwanda's, deepening worries in a region still reeling from the echoes of the 1994 genocide, and where Burundi itself only emerged from ethnic civil conflict in 2005. Regional efforts again to broker peace between Nkurunziza and his opponents are stalled.

Today, Burundi's borders are effectively closed, domestic news outlets shuttered, and the few foreign reporters who make it into the country face arrest or deportation.

In the first months of the crisis last summer, close to a quarter of a million Burundians fled to neighbouring countries, most of them to Tanzania, where 137,000 are now refugees. The number of people leaving Burundi has slowed to roughly 280 a day since the start of 2016, less than a tenth of the numbers fleeing a year ago.

But that trickle of refugees carries with them the freshest accounts of what life is like inside Burundi today, and they often directly contradict the international assumption that because the street protests are over, the crisis is over.

The Sunday Herald, working with UNHCR, the UN Refugee Agency, spent a week talking to Burundian refugees who recently arrived to camps in western Tanzania. The picture they paint is one of a new normal of seemingly endless casual brutality, where there is no apparent logic governing who falls victim: those who oppose the ruling party, and those who support it; young men, and old women; landowners, and the penniless who cannot pay; the well-schooled, and the uneducated.

"I am just a businessman, I never wanted to be involved in politics," says Yamuremye, 32, the scrap-metal dealer from Bujumbura. "Maybe that was the reason they came for us: I did not belong to the ruling party. I have heard that is why people are killed."

He was walking home that Thursday at the end of March after an outing with his family: his wife, Hadija, 25, and their six-year-old son and infant daughter. Friends intercepted him on the road. Don't go home, they said. Men with guns are there.

They spent that night at a mosque. "Sleep was not possible. All I kept thinking was that I hoped everyone at home had managed to escape, that they were alive," Yamuremye said. "Instead, when I ventured there the next day, it was the complete opposite."

In the kitchen he found the body of the friend who lived with them, killed as she cooked dinner – beans, rice, chips – and prepared to take it to the others. "There was blood everywhere, but otherwise it was as it should be, the food, the pots, the tray," Yamuremye said.

In the sitting room, the friend's seven-year-old son lay riddled with gunshots, beside Yamuremye's brothers, aged 15 and 19, who were machine-gunned as they watched television. "There were probably watching football," Yamuremye said. "They loved football." Outside were the bodies of the friend's two daughters, one just turned 10, the other a two-year-old. No-one was spared. His home was looted, his savings stolen.

"There had been lots of strange boys around the neighbourhood," he said, talking from his new home, a plastic tent in a refugee camp. "They looked at me, then they rubbed their hands together like they were pretending to wash clothes. They said, we're going to clean you from this place like this."

Nolasque Nduwimana, a 31-year-old history teacher at a girls' Catholic boarding school, knows why the gunmen came for him. "Yes, I supported the opposition," he said. "Why should that mean I should be killed?"

Friends warned him his name was top of a hit list drawn up at local ruling party committee meetings. He planned to leave, but wanted to complete marking his students' exams first. Like Yamuremye, he almost left it too late.

On Easter Friday, close to midnight, five men broke into his room, forced him to the floor, pointed two machine guns at his head, and were told, "shoot him". In that moment, another teacher in a room down the corridor called out and distracted the gunmen.

Nduwimana took the split second chance to save his life, and fled, barefoot, in his pyjamas, grabbing his spectacles from the nightstand as he leapt through the shower-room window and ran. A bookish man more used to libraries than forests, he spent three days sleeping rough and moving slowly to the border under cover of night.

Disguised as a priest – "the Church is all the militia respect any more," he said – he slipped into Tanzania. For the first days in a refugee camp here, he refused to leave his tent. Even now, his lips stiffen as he talks - trying not to break down. This camp is too close to Burundi, he says. He wants to be moved further away. "People can find me here," he said, as his lips again tightened.

Another man, a student who gave his name as Ernest, told how someone threw a grenade into his family home at the start of March, probably because his father could not pay thugs who circled his neighbourhood extorting residents under the guise of collecting ruling party membership dues.

His parents, three sisters, and a brother were all killed. They had been planning to leave, but left it too late. "Injustice - that is all that thrives in my country today," he said.

Sabine, a grandmother in her 50s who asked that her real name not be published, knows her husband, a local community leader, was killed because he was "loyal, and spoke up against injustice". She had to flee and could not bury him. "I have nightmares - the dogs ate his body," she said.

All of these survivors' mental scars are fresh, and need urgent attention. UNHCR, working with the Tanzanian government and other aid agencies, is providing basic counselling and psychosocial support to refugees, but needs more help.

"The problem is that our donor appeal is so overwhelmingly underfunded that we are only barely able to provide shelter, household items, latrines, showers, I'm talking about the very basics," said Dost Yousafzai, the head of UNHCR's sub-office in the Tanzanian town of Kibondo, 30 miles from the Burundian border and close to the refugee camps.

UNHCR needs £218 million to respond to the Burundi refugee crisis across central Africa but donors including the British Government have so far offered only GBP32 million, less than one in every seven pounds needed.

"With that level of support," Yousafzai continued, "it's things like counselling for people who have survived horrific experiences, or education for children, or care for the disabled and the elderly, or protecting the environment around the camps, which very sadly fall by the way side."

Amid the apparently random violence described by the refugees, one sinister trend emerged: rampant sexual violence, perpetrated mostly against women, but also men. Rape is being used as a punishment at checkpoints in Burundi and at its borders, according to survivors who said they were targeted for associating with the wrong political party, or because of their background or the place they came from.

Nicole, a mother with three young sons, almost made it to the border but was stopped and thrown into a detention centre with dozens of others, where many were assaulted or tortured. She was put in solitary confinement, where she was beaten unconscious then came to with a policeman raping her.

"I was shouting and struggling, but he did what he wanted,” she said, her trembling fingers struggling to catch the tears that rolled down her cheeks. She recalled other officers passing by and walking away. When he was finished, the policeman threw her out of the building. She has not seen her boys since.

Men are also being sexually attacked, a rarity even for the brutal wars of this region. One, a student who gave his name as David, said he was singled out by classmates because he refused to join the Imbonerakure. He was abducted, handcuffed, and repeatedly raped while other men watched. “They would say, ‘you won't join us, so we will show no forgiveness’,” he said. Eventually, he escaped.

Another 36-year-old man was held for a month and is now impotent after he was repeatedly sexually tortured and beaten in the groin, again because he refused to join the militia. Renate Frech, a senior protection officer for UNHCR working in the camps, said the reported sexual violence cases might be "a small number of the reality,” particularly for men.

Many reported sexual or domestic violence cases took place after refugees arrived to the camps: the International Rescue Committee, which works with UNHCR in Tanzania, has helped 1,759 survivors of sexual and gender-based violence that happened after they left Burundi. Numbers of those attacked inside their country are impossible to quantify. Again, with limited international funding to help Burundi's refugees, services to survivors of sexual violence are restricted.

Ernest, the refugee whose family was killed with a grenade, says his country's plight has largely been forgotten. "The world needs to be closer to the people of Burundi, especially those who are still inside the country," he says. "People are dying today, and they will die tomorrow."