An independence vote in east Ukraine will go ahead this weekend as planned, rebels there said Thursday, despite Russian President Vladimir Putin calling on them to postpone it.

"The referendum will happen May 11," the leader of the rebel's self-styled Donetsk People's Republic, Denis Pushilin, told reporters.

A spokeswoman for insurgents in the flashpoint town of Slavyansk simultaneously confirmed to AFP that the vote would happen Sunday.

The affirmations came a day after Putin urged the pro-Russian separatists to put off the vote to give space for dialogue to end the crisis in Ukraine.

After initially being caught off guard by Putin's appeal, the rebels consulted and on Thursday rejected the Russian leader's proposition.

"The date of the referendum will not be postponed," Pushilin said, adding that the council running his republic had voted to go ahead with the regional poll.

An identical referendum has also been called for the neighbouring eastern region around the city of Lugansk. There was no immediate word on whether Lugansk's rebels were maintaining their referendum.

Ukrainian officials earlier Thursday rejected Putin's call for them to halt a military operation against the rebels, who have seized more than a dozen towns.

NATO also says it has no sign that Russian forces massed on the Ukrainian border have been pulled back, as Putin also asserted.