More than 300 Ukrainian troops have crossed into Russia during heavy fighting with pro-Russian separatists.
A Ukrainian security spokesman, Andriy Lysenko, said the 311 soldiers and border guards « had to cross into Russian territory » at the Gukovo checkpoint in eastern Ukraine.
Ukraine is trying to get them back now through diplomatic channels, he said.
Earlier a Russian security official said 438 Ukrainian troops had been given refuge in Russia as « defectors ».