A spokeswoman for EU foreign policy chief Catherine Ashton condemned the separatists' decision to push ahead with Sunday referenda, which would see some 3 million people vote on whether they wish to remain part of Ukraine.

Brussels said the poll would only serve to further complicate the situation.

"Such unauthorized local referenda have no democratic legitimacy and can only lead to further escalation," said EU spokeswoman Maja Kocijancic.

Defiant go-ahead

Separatist leaders in the Luhansk and Donetsk regions (pictured) said on Thursday that they would go ahead with the referenda, despite an appeal by Russian President Vladimir Putin to postpone them.

Meanwhile, officials in Kyiv said the military efforts by Ukraine's interim government against separatists in eastern Ukraine would continue on Friday as Ukrainian troops pressed to retake the city of Slovyansk.

Commemorations raise concern

The tensions coincided Friday with annual May 9 celebrations of the former Soviet Union's World War II defeat of former Nazi Germany in 1945.

Fears arose on Friday that those celebrations could degenerate into nationalist violence. Ukrainian president Arseniy Yatsenyuk said festivities would take place "under war conditions."

In Ukraine celebrations were expected to be muted amid fears of "provocation" from pro-Russian militants.

After attending Friday's celebrations in Moscow, Russian President Vladimir Putin landed in Russian-annexed Crimea.

Gas supply talks to continue

The European Commission said on Friday that officials of the EU, Russia and Ukraine would meet next Monday to continue talks on the future of Russian gas supplies to Kyiv and numerous other European countries. The consultations began in Warsaw last week.

Russia has said Ukraine will have to pay up-front for all future gas deliveries, claiming that it is owed billions of euros in outstanding payments.

rc/ipj (AFP, AP, dpa, Reuters)