Russia endorsed a crushing victory for Ukraine's pro-Moscow rebel leadership after controversial polls on Sunday that the EU slammed as a "new obstacle" for peace in the country's strife-torn east.

The swift acceptance of the results by Russia looked certain to spark a diplomatic firestorm, with a fresh round of Western sanctions against the Kremlin now increasingly on the cards.

The elections may already have been slammed as a farce by the West but those queuing to cast their ballots in east Ukraine's rebel polls on Sunday insisted their voices should be heard. 

"I hope that our votes will change something. Perhaps we will finally be recognized as a real, independent country," Tatyana, 65, said as she waited at a polling station at school number 104 in insurgent stronghold Donetsk.

The Ukrainian military on Sunday reported "intensive" movement of troops and equipment from Russia into the separatist controlled parts of eastern Ukraine.

"There is intensive deployment of military equipment and personnel of the enemy from the territory of the Russian Federation onto territory temporarily controlled by insurgents," Ukrainian military spokesman Andriy Lysenko told a briefing in Kiev.

The leadership of Ukraine's pro-Russian rebels is on course to secure a crushing victory at Sunday's controversial election that Kiev branded a "farce" and which threatened to deepen an international crisis over the conflict.

Alexander Zakharchenko -- prime minister of the self-proclaimed Donetsk People's Republic -- was estimated to get 81 percent of the presidential vote, according to a rebel exit poll released after the ballot ended. 

Pro-Russian separatists in eastern Ukraine hold controversial leadership elections on Sunday that Kiev and the West have refused to recognize and which threaten to deepen the international crisis over the conflict. 

Fighting raged across the region on the eve of the vote, with seven Ukrainian fighters killed and intensive shelling at the ruins of Donetsk airport, a key battleground between the rebels and government forces.

Six Ukrainian soldiers have been killed by pro-Russian rebels in the last 24 hours, a government official said Saturday.

"Our losses as a result of fighting were six servicemen killed and 10 wounded," Volodymyr Polyovy, spokesman for the National Security and Defense Council, said.

Progressive Socialist Party leader MP Walid Jumblat is scheduled to travel to the Russian capital Moscow next week on an official visit, reported al-Joumhouria newspaper on Saturday.

It said that the lawmaker will head to Moscow on Thursday on a three-day visit.

Dutch forensics experts have returned to the site of downed flight MH17 in eastern Ukraine on Friday, where they gathered body parts despite continued clashes in the area, Prime Minister Mark Rutte said.

"Today the circumstances allowed for a small Dutch team... to travel to the crash site and we grabbed the opportunity with both hands," Rutte told journalists at his weekly press briefing in The Hague.

Vitaliy Feshchenko, one of thousands of Ukrainian volunteers fighting pro-Russian rebels, has this message for government leaders back in the capital Kiev: his battle-hardened men might come for them next.

The bearded fighter's warning illustrates the lack of trust Ukraine's young revolutionaries have in President Petro Poroshenko and other politicians promising to drag their country from a corrupt, post-Soviet past into a European future.

Foreign jihadists from more than 80 countries have flocked to fight in Iraq and Syria on an "unprecedented scale", according to extracts of a U.N. report published by Britain's Guardian newspaper on Friday.

Around 15,000 people have traveled to fight alongside Islamic State (IS) and other hardcore militant groups from "countries that have not previously faced challenges relating to al-Qaida," said the report.