International experts have recovered more human remains from the flight MH17 crash site in Ukraine after resuming work earlier today, the Dutch government said.

"The 70 Dutch and Australian experts have finished their work at the MH17 crash site for today," the justice ministry said in a statement.

"All human remains that were found will be taken with them," it said.

The group is the largest to reach the site since flight MH17 was shot down over rebel-held territory on 17 July, killing all 298 passengers on board.

A much smaller group of experts had reached the site yesterday for the first time in several days.

Roads had for days been too dangerous to use because of heavy fighting, frustrating efforts to recover all the victims' remains and push ahead with an investigation.

Earlier, Ukrainian television said 20 servicemen had been killed in an attack by pro-Russian separatists in eastern Ukraine during the night.

However, a military source said the death toll was likely to be lower.

Military officials said a paratrooper unit had come under mortar and tank fire near the town of Shakhtarsk, in the region where a MH17 was brought down.

They said the number of casualties was being checked.

Channel 112 reported in a morning news bulletin: "Twenty Ukrainian paratroopers were killed in a Grad missile attack near Shakhtarsk."

Ukrainian government forces have intensified their military offensive against the rebels in mainly Russian-speaking eastern Ukraine since the airliner came down, killing 298 people.

The separatists are now pegged back in their two main strongholds the cities of Donetsk and Luhansk.

The United States said the separatists probably shot down the plane by mistake with equipment provided by Russia.

However, the rebels and Russia deny the accusation and blame the crash on Ukraine's military campaign to quell the uprising.

Ukraine said its latest combat report shows that Russian aircraft had flown over east Ukrainian territory, the latest of several such accusations in the last few weeks, but Russia has denied such reports.

The United Nations said in a report this week that more than 1,100 people had been killed and nearly 3,500 wounded between mid-April and 26 July.