INTERNATIONAL: At least seven buses carrying surrendered Ukrainian fighters left the Azovstal steel works escorted by pro-Russian armed forces on Tuesday 17th May, a Reuters witness said

Concerns grew on Wednesday for the welfare of more than 250 Ukrainian fighters who surrendered to Russian forces at the Azovstal steelworks in Mariupol after weeks of desperate resistance.

The surrender brought an end to the most devastating siege of Russia's war in Ukraine and allowed President Vladimir Putin to claim a rare victory in his faltering campaign, which many military analysts say has stalled.

Buses left the steelworks late on Monday in a convoy escorted by Russian armoured vehicles. Five arrived in the Russian-held town of Novoazovsk, where Moscow said wounded fighters would be treated.

Seven buses carrying Ukrainian fighters from the Azovstal garrison arrived at a newly reopened prison in the Russian-controlled town of Olenivka near Donetsk, a Reuters witness said.

Russia said at least 256 Ukrainian fighters had "laid down their arms and surrendered", including 51 severely wounded. Ukraine said 264 soldiers, including 53 wounded, had left.

The TASS news agency said the Russian Investigative Committee planned to question the soldiers, many of them members of the Azov Battalion, as part of an investigation into what Moscow calls "Ukrainian regime crimes."

Russian defence ministry video showed fighters leaving the plant, some carried on stretchers, others with hands up to be searched by Russian troops.

There were some women aboard at least one of the buses in Olenivka, Reuters video showed.

While both sides spoke of a deal under which all Ukrainian troops would abandon the steelworks, many details were not yet public, including how many fighters still remained inside, and whether any form of prisoner swap had been agreed.

The Kremlin said Putin had personally guaranteed the prisoners would be treated according to international standards, and Ukrainian officials said they could be exchanged for Russian captives.

Ukrainian Deputy Prime Minister Iryna Vereshchuk said Kyiv aimed to arrange a prisoner swap for the wounded once their condition stabilised.