Moscow: Russia on Thursday claimed its forces had killed two Ukrainian generals and "up to 50 officers" in a strike on the eastern Ukrainian city of Kramatorsk this week.

"As a result of a strike on June 27 on Kramatorsk, two generals and up to 50 officers of the Ukrainian army were eliminated," the Russian defence ministry said in a statement.

"Up to 20 foreign mercenaries and advisers" were also killed, the statement added.

The defence ministry in Moscow claimed Russian forces hit a "point of temporary deployment of the 56th separate motorized infantry brigade of Ukraine's armed forces" with a high-precision strike.

A Russian missile struck a pizza restaurant in Kramatorsk this week, killing 12 people including children and wounding dozens.