At least 10 people were killed on Wednesday when shells hit a school playground and a public transit mini-van in a nearby street in Donetsk in eastern Ukraine, underscoring the fragility of a ceasefire between separatists and government forces.

Teachers managed to lead pupils at school No. 57 into a cellar for safety when shelling started and there were no children among those killed, municipal authorities and witnesses said.

The shelling occurred at 10 a.m. on the first day of the new school year after the 50-60 pupils aged from eight to 10 had already entered the school. The dead included a male biology teacher and the father of one of the children at the school, teachers said.

Apart from those bodies and that of a third person who was identified as a separatist fighter, Reuters correspondents saw a further six bodies in the burnt-out mini-van and on streets nearby.

The regional administration said a total of 10 people had been killed in the shelling in the city, a stronghold of Russian-backed rebels waging a separatist rebellion against the pro-Western government in Kiev. Rebels put the number of dead at 12, saying two victims had been removed from the scene.

Nine others were wounded, seven of whom were taken to hospital, the municipality said in a statement on its website.

City authorities blamed the shelling on the rebels and the separatists blamed it on government forces. It interrupted a fragile ceasefire in a conflict in which about 3,500 people have been killed, according to U.N. figures.

BROKEN GLASS

Ukrainian President Petro Poroshenko said last week there were clear signs that the ceasefire that came into force on Sept. 5, the cornerstone of his peace plan to end six months of conflict, was working.

But it has begun to fray with the deaths on Monday and Tuesday of nine Ukrainian servicemen in clashes with separatists.

The school is in a city district a few kilometres from the city's main airport where separatists have been trying to dislodge government forces for some days.

Since the rebellions erupted in eastern Ukraine in April and shelling began in Donetsk, authorities have introduced distance-learning courses for children to allow them to stay at home. School No. 57 has capacity for 400 children although only the 50-60 assembled for classes on Wednesday.

There were pools of blood inside the school and the floor was strewn with broken glass and overturned school tables.

Lidia Sheiko, who teaches Russian at the school, said: "It was a nightmare. There was glass flying everywhere. The children got frightened and began to cry."

Near the shelled school, a Reuters team saw two charred bodies in the mini-van, two more on the pavement and another two on the street about 20 metres (yards) away.

A car had also been hit and destroyed. Rebels at the scene said two people had been killed in it and their bodies had been taken away.

A commander of a rebel unit, Viktor Khalyava, said the school was hit by five Uragan rockets fired by the Ukrainians. "It was a targeted strike on the school," he said.

The municipal authorities however blamed the attack on the school and on the minibus on forces of the rebel "Donetsk People's Republic."