Fighting eased in the Donetsk region on Monday after Ukraine launched a major offensive and claimed to clear pro-Russian rebels from most of the airport outside the key eastern city.

There were a number of sporadic explosions overnight, but the violence seemed to be far less than in previous days, when heavy clashes shook the area around the airport and shelling moved closer toward the city centre, killing at least 10 civilians.

It was unclear if the break in the fighting would last. Monday was also an important religious feast in Ukraine, with Orthodox Christians celebrating Epiphany.

Kiev and Moscow traded blamed for the complete breakdown of a September ceasefire in recent days, while UN Secretary-General Ban Ki-moon voiced alarm and called for an immediate end to the violence.

The UN Security Council is due to discuss the worsening crisis at a meeting on Wednesday.

With rebels at one point claiming to control the airport, Ukraine launched a massive counter-offensive with tanks and other heavy artillery on Saturday which continued into Sunday.

Ukraine's military claimed on Sunday afternoon to have cleared out most of the airport, but there was no independent verification of their account, with journalists unable to approach the facility.

The conflict has killed more than 4,800 people since April last year and has become Europe's worst humanitarian crisis since the Balkan wars of the 1990s.

Ukraine and Western nations say Russia has supported the rebels with troops and weapons, charges Moscow strongly denies despite witness claims to the contrary.