People walk past the site of an explosion in Kyiv, Ukraine. File/AP

A British aid group says it believes two Britons have been abducted by Russian forces in southeastern Ukraine.

Dominik Byrne, the co-founder and chief operating officer of the Presidium Network, told The Associated Press on Friday that the men were last heard from on Monday.

Byrne said the men were taken while trying to carry out an independent evacuation in Dniprorudne, near the city of Zaporizhzhia, some 470 kilometres (290 miles) southeast of Kyiv.

Byrne said the family that the two men had been trying to evacuate later were interrogated by Russian forces, who asked them about the "British spies.” Bryne said the family later escaped to Poland.

Byrne identified the men as Paul Urey and Dylan Healy. He said they had been operating on their own in the war zone and hadn’t been associated with any aid group.

The British Foreign Office did not immediately respond to a request for comment. Russia hasn’t acknowledged taking the men.

Associated Press