Ukraine government and rebels blame each other for attack, which has killed evacuees trying to escape the conflict

Dozens of people, including women and children, were killed on Monday when a convoy carrying refugees was hit by rocket fire near the eastern city of Luhansk, a Ukrainian military spokesman said.

Government forces and pro-Russian rebels accused each other of the attack on the vehicles, which were evacuating civilians from the towns of Khryaschuvate and Novosvitlivka.

"The rebels were expecting the convoy and destroyed it entirely. We haven't been able to count the number of victims ... dozens (were killed)," spokesman Andriy Lysenko said in a briefing to journalists.

Another military spokesman, Anatoly Proshin, said that evacuees were being transported by military vehicles flying white flags, which were hit by mortars and Grad rockets.

"As a result, there were a huge number of casualties. People were burned alive in the vehicles that were taking them out," Proshin told the Ukrainian Pravda newspaper.

But Andrei Purgin, deputy prime minister of the self-declared Donetsk People's Republic, said that the rebels did not have the ability to send Grad rockets to the area where the convoy was hit, and said that government forces have been bombarding that road with Grad rockets and airstrikes.

"It seems they've now killed more civilians, like they've been doing for months now," Purgin told Reuters.

The location of the convoy.

The US state department condemned the attack but said that it could not confirm who was responsible. "We strongly condemn the shelling and rocketing of a convoy that was bearing internally displaced persons in Luhansk and express our condolences to the families of the victims," spokeswoman Marie Harf said. "Sadly, they were trying to get away from the fighting and instead became victims of it."

The BM-21 Grad, whose name means "hail" in Russian, is a fearsome weapon that can fire more than two dozen incendiary rockets in quick succession but it is notoriously inaccurate. Both sides have been known to deploy it in the conflict.

Proshin also said that government forces would fully encircle Luhansk within the next 24 hours and would then begin an operation to capture the city. Residents there have already been without water, electricity and mobile phone connections for two weeks; Moscow has sent a convoy to a nearby border crossing carrying humanitarian aid.

There were reports on Monday that suggested street fighting had broken out in Luhansk. Following the news this weekend that government forces had raised a Ukrainian flag over a police station there, Lysenko said Kiev's troops had taken over "part of the city". But rebel spokesman Konstantin Knyrik was quoted by pro-Russian news outlets saying that rebels had reconquered some areas and removed the Ukrainian flag.

"According to the rebels in the city, fighting is ongoing in territory equal to about one-third of Luhansk. Certain sections of streets are constantly changing hands," Knyrik said.