OSCE meeting on Ukraine

The US mission to the Organization for Security and Cooperation in Europe confirmed the special session on Twitter Thursday, saying it "will focus on latest developments in Ukraine."

There has been increasing concern in Kyiv and the West about Russia's possible direct participation in the conflict, despite Moscow's repeated denials of allegations that its troops are on the ground.

The US ambassador in Kyiv earlier accused Russia of being "directly involved" in fighting.

"An increasing number of Russian troops are intervening directly in fighting in Ukrainian territory," Geoffrey Pyatt wrote on Twitter. He said Moscow was "directly involved in the fighting" and had sent in its "newest air defense systems including the SA-22."

Novoazovsk taken by rebels

This comes as separatists have reportedly entered the town of Novoazovsk, which lies along the road connecting Russia to the Russia-annexed Crimean peninsula.

A pro-government militia fighter told Reuters by telephone that the rebels were backed by Russian troops.

"There is military equipment in Novoazovsk which came across the border two days ago from Russia. The equipment is carrying the flags of the DNR (Donetsk People's Republic) rebels but they are regular Russian forces," he said.

In Donetsk, local authorities Thursday said that mortar bombardments had killed at least 11 civilians and wounded 22 more over the past 24 hours.

hc/tj (AFP, AP, Reuters)