Merkel: ‘Grave concern’ on new Russian tanks in Ukraine

She also voiced worry about “ongoing fighting and the deteriorating humanitarian situation" in the separatist-controlled regions.

For his part, Poroshenko warned Merkel of a “substantial rollback in the implementation of the Minsk protocol [a September ceasefire accord], which leads to further escalation of the conflict”.

He complained that Russia keeps sending what it calls “humanitarian aid convoys” into Ukrainian territory without Ukraine’s permission.

He also noted that Russia is delaying payments for gas transit for September and October in a development which augurs badly for the implementation of an EU-brokered agreement on winter supplies.

The same day, Andriy Lysenko, a spokesman for the Ukrainian military, said on TV that 32 Russian tanks, 16 artillery systems, and 30 trucks carrying ammunition had entered Ukraine’s Luhansk region.

“Supplies of military equipment and enemy fighters from the Russian Federation are continuing,” he noted.

But the Russian foreign ministry, in a statement one day earlier, accused the Ukrainian side of violating peace accords.

“Instead of de-escalating tensions, Kiev has stepped up hostilities and is using heavy weaponry in the southeastern regions, which has claimed thousands of lives and led to large-scale destruction”, it said.

The threat of military escalation comes after pro-Russian fighters in the self-proclaimed Donetsk and Luhansk republics installed new leaders and “MPs” in "elections" rejected by the EU, the UN, the OSCE, and Nato.

Merkel had earlier said the votes would lead to another “frozen conflict” in Europe and warned, in a statement on Wednesday, that the EU should consider expanding its blacklist to include “certain personalities who now, because of these illegitimate elections in eastern Ukraine, have responsibility”.

The Russian foreign ministry said at the time that it “respects the expression of will of the south-eastern [Ukrainians]”.

But a Kremlin aide, Yuri Ushakov, told press on Friday that its use of the word “respect” instead of the more official word “recognise” is important in the way the EU should react to Russia’s treatment of the separatists.

“The word 'respect' was chosen deliberately … we fundamentally respect the will of the voters”.