DONETSK, Ukraine -- Fighting raged Sunday on the western outskirts of Donetsk as the advancing Ukrainian army tried to seize control of the rebel stronghold. In danger of being encircled, the separatists renewed their calls for Russia to send troops to their aid.

To support their operations, the pro-Russian fighters have been confiscating vehicles and food from residents and businesses in Donetsk. The centre of the major industrial city is all but deserted, with few people or cars on the streets and most stores and restaurants closed.

A spokesman for the Ukrainian military operation, Alexei Dmitrashkovsky, told The Associated Press that government soldiers were fighting Sunday to hold positions they had taken on the edge of Donetsk, but were meeting resistance.

In the part of the city closest to the fighting, an artillery shell hit a school overnight, but no one was reported hurt.

"The shell went through the roof and exploded inside the building, setting off a fire, but we still don't know who fired it," said Dmitry Levonchik, a 45-year-old coal miner. "Who needs this war? What are they fighting for?"

The sound of gunfire and explosions was heard just to the west.

Pavel Gubarev, the self-proclaimed governor of the separatist Donetsk region, said the rebels would win quickly if Russia sent troops.

"Of course it would be great to see Russian peacekeepers here: strong artillery units, tank brigades," Gubarev said. "This war would be over in a day, maybe two."

Ukraine and the West say they have evidence that Russia is arming the separatists. Russia denies this and describes the Russian citizens fighting in eastern Ukraine as volunteers.

The conflict began after the Moscow-leaning president was ousted in February following months of street protests and a new pro-Western government took power in Kyiv. Alarmed by the prospect of Ukraine moving closer to the European Union and NATO, Russian President Vladimir Putin fomented the pro-Russia insurgency in the mostly Russian-speaking east with the apparent aim of winning an agreement that would allow Moscow to maintain its influence in Ukraine.

If he is unable to win such a compromise and the Ukrainian army continues to take back rebel-held cities and towns, Putin may come under increased pressure to intervene militarily.

Many Donetsk residents have counted on help from Russia.

"What is Putin waiting for? He inspired us to fight," said Ilya Sumyatin, a 38-year-old separatist fighter. "We had hoped for help from Russia, but we have been abandoned. Our strength is nearing an end and the Ukrainian army is advancing."

The separatist fighters in Donetsk have proclaimed the right to confiscate any "strategically important resources" to support their operations.

On Sunday, a major trucking company that delivers to grocery stores said it was suspending its operations in Donetsk after rebel fighters raided its warehouses. The company, Deliveri, said in a statement on its website that the goods stolen Saturday evening were worth about $840,000.

Viktor Okhramovich, who drives a minibus taxi, said the separatists seized his vehicle. "What am I supposed to do? I have nowhere to go to complain," he said.

With the Ukrainian army approaching the city, many Donetsk residents have become reluctant to express support for the rebel fighters.

"Donetsk has turned into a dark hole where you can be taken prisoner, robbed, killed or have your home destroyed," said Inna Statsenko, a 52-year-old bank employee, who said she once supported the separatists.

"Now I see that nothing good will come of this. It's time to escape this nightmare," she said, pointing to a nine-story apartment building that had been hit by shelling.

After not seeing much fighting other than a rebel attempt in May to seize the city airport, Donetsk came under shelling last week. About 200 apartment buildings and 2,300 private homes remain without electricity, city officials said.

An estimated 200,000 people in the city of 1 million have left their homes, said Ivan Volchok, an official in the regional administration who said his department helps organize travel to safer places in Ukraine. The Donetsk airport is closed, but buses and trains are still running.

Fighting also has been heavy around Luhansk, the second-largest city still held by the rebels. City officials said Sunday in a statement that three civilians had been killed during the past day.

The ongoing battles had delayed the start of an international search for body parts still lying in the fields where Malaysia Airlines Flight 17 was shot down on July 17 with 298 people on board.

Dutch and Australian experts were able to begin their search Friday. Early Sunday, the remains and personal belongings they had found so far were delivered in refrigerated trucks to the city of Kharkiv. The recovered remains will be checked there before being flown to the Netherlands.

Pieter-Jaap Aalbersberg, the head of the recovery mission, said in a statement late Saturday that the entire area around a chicken farm near the village of Hrabove has now been searched and the experts will move to other sites where aircraft wreckage was found. He previously estimated that the entire search would take at least three weeks.