Six Ukrainian rebels have been killed while trying to collect the bodies of comrades who died under Ukrainian army fire earlier this week near the Donetsk airport, Ukrainian separatist leader Denis Pushilin says.

"They died trying to take back the Ukrainian airport, and our boys were trying to get their bodies out," Pushilin told Reuters via telephone on Saturday, without giving further details of the violence. He said the six had died during the day on Friday.

Ukrainian forces regained control of the airport in the east of the country on Monday last week, killing at least 50 separatists, a day after the country's presidential election which gave Petro Poroshenko an overwhelming victory.

It was the first time the Ukrainian side had unleashed its full force on the pro-Russian two-month rebellion, caused partly by the ouster of a Moscow-friendly president.

Though fighting has died down for now in Donetsk, the standoff over the city airport remained unresolved on Saturday with amateur video footage showing a cargo plane taking off and releasing decoy flares as it was fired at from the ground.

Regional newsagency Interfax cited the prime minister of the self-styled Donetsk People's Republic as saying the separatists would ask the International Red Cross to remove corpses by the aiport. It was unclear how many remained.

A spokesman for the Kiev-led "Anti-terrorist operation" or ATO said earlier in the day two new attacks on the airport had been repelled by Ukrainian forces with no injuries to their side, Interfax reported. It was not clear whether the attacks were in fact attempts by separatists to clear bodies.

Pro-Russian protests

Meanwhile, in central Donetsk on Saturday, news agencies reported at least 1,000 people gathered in the city's Lenin Square, waving Russian flags and calling on Russia to protect them from the Ukrainian military.

"I have no other objective but to make Donbass a part of Russia," said Alexander Boroday, the self-styled prime minister of the republic, referring to a wider eastern Ukrainian region containing heavy industry, coalmining and steel works.

Further from the city centre, rebels built up two new barricades overnight: by the sprawling residence of multi-billionaire Rinat Akhmetov, the country's richest man, and by the headquarters of the heavily armed, pro-Russian Battalion Vostok militia.

At a cemetery in the adjacent town of Makievka, 10 rebels fired into the air to honour their commrade, Vasily Burov, 46, killed on Thursday in a firefight with the Ukrainian army.