Tens of thousands of people marched through central Moscow on Sunday to demonstrate against the fighting in Ukraine and Russia's alleged complicity in the conflict.An Associated Press reporter estimated the crowd at about 20,000, although the city police department put the number at about 5,000.

The demonstrators chanted slogans including "No to war" and "The junta is in the Kremlin, not Kyiv." The latter refers to Russia's contention that the ousting of Ukraine's former Russia-friendly president was a coup.

The fighting between Ukrainian forces and pro-Russia separatists in eastern Ukraine that erupted after the ouster has killed more than 3,000 people. Ukraine and Western countries claim Russia is supplying troops and equipment to the rebels, which Moscow denies.

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"Our country is acting as an aggressor, like Germany in the war," said demonstrator Konstantin Alexeyev, 35.

The Ukraine conflict has boosted nationalist sentiment among Russians, many of who regard eastern Ukraine as rightfully a part of Russia, and coverage of the crisis on state-controlled television channels has skewed strongly against the Ukrainian authorities.

"I am concerned about the rhetoric on our TV channels, which disseminate anti-Ukrainian sentiment," said 50-year-old demonstrator Ludmila Shteigervalt. "Ukraine is a friendly country. We should just leave it alone."

At least one scuffle broke out between protesters and nationalists who unfurled a banner denouncing "The March of Traitors."

In Kyiv, a Ukrainian security official said attacks by Russia-backed rebel fighters are continuing despite a cease-fire called for by both sides more than two weeks ago.

Col. Andriy Lysenko, a spokesman for Ukraine's national security council, said two Ukrainian servicemen and about 40 rebels had died in clashes over the past day. He said the fighters fired on Ukrainian positions at 22 locations and that they fired artillery at the airport in Donetsk, the largest rebel-held city.

The city council of Mariupol, a strategically vital city on the coast of the Sea of Azov, said sporadic shelling of points on its outskirts took place during the night and into Sunday daytime. There were no immediate reports of injuries there.

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A cease-fire was called on Sept. 5, but has been violated repeatedly. Negotiators from Ukraine, Russia, the rebels and the Organization for Security and Cooperation in Europe last week tried to further the peace process with an agreement calling for both sides to halt their advances and for pulling back heavy artillery in order to create a buffer zone.

But Lysenko said the cease-fire violations are obstructing fulfilment of the buffer zone plan.

"The first point (the cease-fire) is not being fulfilled so far, so we're not talking about the other points," he said.

Along with pulling back the heavy weapons, the plan also calls for the withdrawal of foreign fighters and for all military flights over the combat area to be banned.