Russian forces have begun storming a steel plant in the besieged port city of Mariupol on Tuesday, Ukrainian officials have claimed. 

It comes after more than a hundred of civilians were evacuated from bunkers below the Azovstal steelworks with support from the UN.

Osnat Lubrani, the UN humanitarian co-ordinator said in a statement that, thanks to the evacuation effort: “One hundred and one women, men, children and older persons could finally leave the bunkers below the Azovstal steelworks and see the daylight after two months.”

However, those remaining in the underground tunnels and bunkers may now face invading Russian troops despite Russian president Vladimir Putin ordering his military not to storm the facility two weeks ago. 

The deputy commander of the Azov Regiment holed up in the plant confirmed that Russian troops were invading the Azovstal plant. 

Sviatoslav Palamar, said the Russians were mounting a heavy assault on the plant with “the support of armoured vehicles and tanks, with attempts to land troops from boats and a large number of infantry”.

“We’ll do everything that’s possible to repel the assault, but we’re calling for urgent measures to evacuate the civilians that remain inside the plant and to bring them safely,” he said.

Another Ukrainian commander Denys Shelga said: "Our fighters are repelling all attacks."

HeraldScotland: Civilians in Mariupol line up to receive humanitarian aid (Alexei Alexandrov/AP)Civilians in Mariupol line up to receive humanitarian aid (Alexei Alexandrov/AP)

He added that throughout the night, the plant was hit with naval artillery fire and airstrikes. Two civilian women were killed and 10 civilians were wounded, he added.

The assault began almost two weeks after Russian president Vladimir Putin ordered his military not to storm the plant, but rather block it off.

The assault came as the first convoy of evacuees from the plant arrived in the Ukrainian-controlled city of Zaporizhzhia, some 140 miles (230km) northwest of Mariupol.

At a reception centre, stretchers and wheelchairs were lined up, children’s shoes dangled from a shopping trolley and a pile of toys waited for the first convoy of civilians whose evacuation was being overseen by the United Nations and Red Cross.

The arrival of buses and ambulances was a rare glimmer of good news in the nearly 10-week conflict that has killed thousands, forced millions to flee the country, laid waste to towns and cities, and shifted the post-Cold War balance of power in eastern Europe.

HeraldScotland: Women walk past a destroyed apartment building in Mariupol (Alexei Alexandrov/AP)Women walk past a destroyed apartment building in Mariupol (Alexei Alexandrov/AP)

“Over the past days, travelling with the evacuees, I have heard mothers, children and frail grandparents speak about the trauma of living day after day under unrelenting heavy shelling and the fear of death, and with extreme lack of water, food and sanitation,” Ms Lubrani said.

“They spoke of the hell they have experienced since this war started, seeking refuge in the Azovstal plant, many being separated from family members whose fate they still don’t know.”

In addition to the 101 people evacuated from the steelworks, another 58 people joined the convoy in a town on the outskirts of Mariupol, Ms Lubrani said.

Some decided not to travel all the way to Zaporizhzhia, where a total of 127 people arrived on Tuesday, she added.

The Russian military said earlier that some evacuees had chosen to stay in separatist areas. In the past, Ukraine has accused Moscow’s troops of taking civilians against their will to Russia or Russian-controlled areas — something the Kremlin has denied.

Mariupol has come to symbolise the human misery inflicted by the war. A Russian siege has trapped civilians with little access to food, water and electricity, as Moscow’s forces pounded the city to rubble.

The plant — where about 1,000 civilians sought shelter along with some 2,000 fighters who have refused to surrender — has particularly transfixed the outside world.

Deputy prime minister Iryna Vereshchuk told reporters on Tuesday that a few hundred civilians remained at the plant — but it was unclear whether a new evacuation would be organised.