A key round of peace talks between Ukraine's government and pro-Russian armed groups, due to take place in Minsk on Friday, Dec 26, has been called off, Belarusian officials said.

No immediate reason was given by the Belarusian Foreign Ministry, according to BBC News.

The talks began on Wednesday to try to end the conflict in eastern Ukraine which has left 4,700 dead. A ceasefire and framework peace deal were announced in Minsk in September but neither has been properly observed.

The latest talks also included Russia and the Organization for Security and Cooperation in Europe (OSCE).

Friday's round had been expected to tackle issues including the withdrawal of heavy weapons from the front line, the exchange of prisoners and ending Ukraine's economic blockade of rebel-held areas.

Belarusian Foreign Ministry spokesman Dmitry Mironchik told AFP: "There will be no contact group meeting today," but he added that "Belarus is always ready to offer [Minsk] as a negotiations venue." Wednesday's talks focused on troop withdrawals and aid, although no details of any progress emerged.

A day earlier, Ukraine's parliament had voted to work towards membership of NATO, a move heavily criticized by Russia.

Russia's Deputy Defense Minister Anatoly Antonov accused NATO members of "trying to turn Ukraine into a front line of confrontation with Russia".