EU-brokered Ukraine truce 'holding', but at risk

He said there are “numerous unconfirmed allegations regarding ceasefire violations”.

But he added: “Based on what it could hear overnight and what it could observe during the daylight, the SMM notes the ceasefire was overall respected over the first 12 hours of its implementation”.

He said the main exception was Debaltseve, where artillery fire “started” at 10am local time.

He noted that an OSCE patrol tried to enter the town, a strategic railway hub, but was “refused access” by Russia-controlled fighters.

He added that Mariupol, a strategic port in east Ukraine, is quiet. He said Donetsk witnessed one mortar round, three rocket attacks, and some small arms fire between midnight and 1am. His staff heard “outgoing” artillery rounds from Russia-occupied Lugansk at 1.45am. They also heard artillery fire in Raihorodka at 10.35am.

Shortly before midnight on Saturday, Ukrainian president Petro Poroshenko ordered his troops to stop hostilities in line with a deal brokered by the French and German leaders with Russia in Minsk last week.

Poroshenko denied reports that thousands of Ukrainian soldiers are trapped in Debaltseve, calling the claims a “sick hallucination”.

But he said the town is a potential “springboard” for future attacks on Ukraine, adding: “the tense situation … poses a great threat to the ceasefire regime”.

For his part, Aleksandr Zakharchenko - the head of the self-proclaimed Donetsk People’s Republic - said the Minsk deal doesn’t apply to Debaltseve because the town is no longer part of Ukrainian territory.

He said his fighters have encircled 8,000 Ukrainian soldiers in the town, adding: “We will block all attempts to break out”.

Russia, which claims it is not involved in the conflict, has not issued a statement on the situation.

But it said it delivered another 900 tonnes of what it called “humanitarian cargo” to Donetsk.

The convoy is the latest in a line of supply trucks which go back and forth across the Russia-Ukraine border with no Ukrainian or international supervision.

EU leaders at a summit last Thursday gave “cautious” approval to the Minsk ceasefire plan.

But they warned that if Russia violates the pact they will impose further economic sanctions.

One senior EU source said: “We are extremely sceptical that the Minsk agreement will end the conflict”.

A second EU source noted that Russia is likely to seize Debaltseve and Mariupol before it really freezes the fighting.

The contact noted that Russian leader Vladimir Putin in Minsk told his French and German counterparts his forces need “at least” 10 days to capture the two cities.

He tried to delay the ceasefire deadline until they fell, but later agreed to the 15 February deadline on paper.