The main members of the so-called contact group – Ukrainian former president Leonid Kuchma, a Russian diplomat and an Organization for Security and Cooperation in Europe official - met at a state residence in the Belarussian capital Minsk, where they were joined by two separatist officials.
The sides have held only one inconclusive meeting since agreeing a ceasefire last September as part of a 12-point blueprint for peace. Much-violated from the start, that truce collapsed completely with a new rebel advance last week.
Both sides have accused each other of deadly artillery and mortar strikes on civilian targets in the past two weeks, including on a cultural centre in the main regional city of Donetsk on Friday which killed at least five people waiting for humanitarian hand-outs.
The September Minsk peace plan also called for tighter control of the joint Russia-Ukraine border, through which Kiev says Moscow is funnelling fighters and equipment, and the
freeing of prisoners held by the sides. Much has changed on the ground, however, since September.
The separatists have set up self-proclaimed 'people's republics' while their forces, which Kiev says are supported by 9,000 Russian regular troops, have seized more than 500 square km (193 square miles) of territory beyond that agreed in the Minsk talks and threaten to seize control of the east's two main regions entirely.
Heavy shelling continued on Saturday in Ukraine's eastern regions as the separatists sought to tighten a circle around government forces clinging on to control of the strategic rail and road junction of Debaltseve.

Regional police chief Vyacheslav Abroskin, in a Facebook post, said 12 civilians had been killed on Saturday by separatist artillery shelling of the town, which lies to the north-east of Donetsk.

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