An envoy from the Organization for Security and Cooperation in Europe has voiced regret over the intransigence of Russia-backed rebels in eastern Ukraine, who have insisted on holding local elections in defiance of the Ukrainian government.

Ambassador Martin Sajdik, the OSCE's representative at the Contact Group talks, told reporters after Tuesday's round of talks in the Belarusian capital Minsk that the rebels said they would hold the vote in October and November as they planned earlier.

The Ukrainian government dismissed the planned election as a sham and insisted that they could only be held in accordance with Ukrainian law.

February's peace agreement has helped reduce hostilities between Ukrainian government forces and the rebels, but political issues have remained unsettled and the parties have accused each other of breaching the deal.