This morning there was an attempt by the Russian military, in the guise of D----s fighters, to open a new area of military confrontation in the southern Donetsk region," spokesman Andriy Lysenko told journalists.

D----s is the local name given to Ukraine's industrialised east and the focal point of the pro-Moscow separatist insurgency.

But Foreign Minister Sergei Lavrov dismissed the reports of a Russian incursion, saying: "I haven't heard about it, but there has been more than enough disinformation about our invasion. No doubt some foreign newspaper will print that 'news' tomorrow."