Maggie Tookey, 64, field operations director of Edinburgh Direct Aid, said Islamic militants have targeted innocent people in Lebanon who are fleeing from Iraq and Syria as extremist forces under the jihadist group Islamic State advance across the region.
Ms Tookey, speaking from Arsal, in the Bekaa Valley, Lebanon, said the international aid charity had been supporting tens of thousands of Syrian refugees in the small town on the mountainous border with Syria.
The Sunni militants of Islamic State, who see Iraq's majority Shi'ites as apostates who deserve to be put to death, have killed fellow countrymen and women fleeing the violence, with 20 dying in one camp alone.
Ms Tookey said Arsal - where 100,000 refugees have headed in recent months, adding to the 30,000 population - had become a "violent focus" of the new crisis caused by the Muslim extremist movement.
She said: "Camp after camp after camp housing the refugees in tents and flimsy plastic shelters have been destroyed in the fighting between Islamic State and the Lebanese army, with militiamen from the Lebanese Shia organisation Hezbollah also joining the mayhem.
"The majority of the Syrian refugees are Sunni Muslims.
"In some of the camps there is nothing left - just ashes and refugees kicking around in the mess to see if any useful scraps have survived.
"At the first camp I met a young father in huge distress because both his tiny babies had died in the flames that engulfed it.
"The conflagration must have been total because the tents and shelters were packed closely together.
"The fires must have raged through, with little chance of escape.
"Rescuers have pulled out scores of bodies from the ashes and the search continues."
She continued: "At the second camp I reached I and my Lebanese helpers were mobbed by desperate refugees.
"Seventy families were living in only nine surviving tents. They had no food, no spare clothes, no mattresses or blankets. As I waited for the aid from the convoy to be sorted and distributed, I negotiated from three nearby villages three water trucks and bread for about 600 people.
"A Syrian co-worker and I stuffed the bread in every corner of his car and when we made the delivery it was as though we were delivering handfuls of gold."
The field worker who has delivered aid to Gaza, Sri Lanka and Pakistan said: "So far, following an Islamic State withdrawal, I have been the only international aid worker to have reached Arsal.
"I came in a convoy of trucks carrying eight tonnes of food, medicines and clothes from Scotland.
"Part of the convoy was a Land Rover ambulance donated by the people of Scotland."
Ms Tookey added: "Fortunately, a school for refugee children, in an old building we have been supporting with books and desks, has survived almost intact, as is the clinic we manufactured from one of our shipping containers.
"The headteacher's 13-year-old son, whom I remember as a pleasant lad playing football, was hit by shrapnel during the fighting and had to have a leg amputated."
Denis Rutoviz and Dr Colin Cooper, of Edinburgh Direct Aid, shepherded the aid through and stayed in Lebanon for 10 days.
The UK Department for International Development said yesterday it would give £3 million to help Mercy Corps - another Edinburgh charity operating extensively in the region including Lebanon - Save The Children, International Rescue Committee and Action Against Hunger provide food, medicines and water to more than 100,000 people in northern Iraq.
Michael McKean, of Mercy Corps, said it meant workers could "move very quickly and there are no delays getting people the help they need".