Nations called Friday on all sides in Ukraine to fully uphold a European-brokered ceasefire after an upsurge of fighting raised fears of a return to all-out conflict.

Nations called Friday on all sides in Ukraine to fully uphold a European-brokered ceasefire after an upsurge of fighting raised fears of a return to all-out conflict.

"The ceasefire must be fully respected and the protection of civilians a priority," UN political chief Jeffrey Feltman told an emergency Security Council meeting.

"We are either looking at a return to a deepening intractable conflict or a momentary upsurge in parts of the conflict zone," he told the 15-member council.

"We cannot afford either scenario."

The Security Council was convened at Lithuania's request amid fears that the four-month ceasefire brokered by France and Germany was under threat.

On Wednesday, at least 28 people were killed in fighting in the town of Maryinka, in some of the worst clashes since the truce was agreed in February.

"Developments around Maryinka are worrying," the deputy head of the OSCE monitoring mission, Alexander Hug, told the council.

The fighting suggests "that the military track has not been abandoned in favor of the political one."

Hug reported that ceasefire violations are becoming more frequent and more severe, and noted that the deliveries of Grad rockets and rocket launching systems are "cause for added concern."