Russia also says that Western military vehicles were used in the incursion.

It posted pictures of destroyed US vehicles apparently at the scene of the fighting but some Ukrainian military experts and bloggers have suggested they could have been staged.

The US said it was skeptical that reports of US-supplied weapons being used in the incursion were true and did not “encourage or enable strikes inside of Russia”.

But Kremlin spokesman Dmitry Peskov said the vehicles were evidence of growing Western military involvement in Ukraine.