Dozens of refugees were reported killed in an attack on a civilian convoy fleeing fighting in eastern Ukraine, with the Ukraine government and pro-Russian separatists both blaming each other.

Andriy Lysenko, a Ukraine military spokesman, said the barrage took place on Monday morning between the towns of Khryashchuvate and Novosvitlivka, near the besieged rebel-held city of Luhansk.

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Describing the attack as a "bloody crime", he said: "A lot of people have been killed including women and children. The number of the dead is being established." He added that the toll could be in the dozens.

Mortar bombs and artillery were reported to have hit the convoy, with many vehicles set alight.

However, Andrei Purgin, a self-proclaimed deputy prime minister of separatists in the Donetsk region, insisted the attack was not by his forces.

"If someone was killed, it wasn't us but the Ukrainian military," he told the AP news agency. Other separatist leaders said there was no evidence an attack had taken place.

Fighting across eastern Ukraine has forced nearly 344,000 people to flee
their homes, according to UN figures released Friday.

The Ukrainian army reported new successes overnight, building on a weekend breakthrough when troops raised the national flag in Luhansk, which was held by pro-Russian separatists since fighting began in April. 

A Ukrainian fighter jet has been shot down while flying over rebel-held territory in the restive east, according to Ukrainian military.

'No deal in Berlin meeting'

Sergey Lavrov, Russia’s foreign minister, said on Monday that all issues around a Russian humanitarian convoy to relieve needy areas of eastern Ukraine had been resolved, adding that he expects it to cross the border in the near future.

Speaking Monday at news conference in Berlin, he, however, said that no progress had been made in his talks in Berlin on Sunday with the Ukrainian, German and French foreign ministers on a ceasefire or a political solution.

Russia says it would like a ceasefire to transport aid to people trapped by the fighting in eastern Ukraine. A 280-truck convoy sent by Russia and carrying tonnes of humanitarian aid has been stalled at the Ukrainian border since last week, as Kiev has insisted on formalities so it can be properly distributed by the Red Cross.