Thousands of Russians have rallied in Moscow in protest against the armed conflict in eastern Ukraine, in the first major anti-war rally since the standoff between Kiev and pro-Russian rebels started last year.

Russian and Ukrainian flags were seen flying in the crowd, as banners read "We are together", "Putin, I'm sick of your lies" and "I don't want a war with Ukraine." Protesters were heard chanting "No to war."

"Putin means war, he is the leader of the party of war," one of the organisers and prominent Kremlin critic Boris Nemtsov said by phone. "If there are a lot of us today, he will back down, because he is afraid of his own citizens, and only the Russian people can stop Putin."

The armed conflict, which Kiev and the West blame on Russia's support of the separatist armed groups in eastern Ukraine, has killed more than 3,000 people since April.

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A ceasefire agreement signed on September 5 has been repeatedly violated, and a memorandum signed on Saturday to create a buffer-zone between the warring sides is hoped to consolidate the peace efforts. 

Moscow police said 5,000 people attended the march.

A Reuters correspondent said at least several thousand protesters packed Moscow's central Tverskaya street on Sunday afternoon amid increased police presence, which included a helicopter overseeing the area.

Buffer-zone deal

The Minsk memorandum, which was signed on Saturday by both parties and endorsed by Moscow's Kiev ambassador and an OSCE envoy, requires the withdrawal of all "foreign armed groups" and mercenaries from the conflict zone.

NATO's top general Philip Breedlove insisted that their intelligence showed that the Russian troops "are still inside Ukraine", although Moscow has denied sending in any forces across the border.

Ukraine has insisted on keeping its troops on the frontlines until the ceasefire is fully intact, following heavy clashes between pro-Russian rebels despite agreement.

"If [Ukrainian forces] are withdrawn, it will be done simultaneously with the Russian troop withdrawal." said Andriy Lysenko, the National Security and Defence Council spokesman.

Lysenko said the first point agreed in the Belarussian capital referring to a mutual ceasefire had to be respected before the rest of the plan could be implemented.

"But the first point has not yet been fulfilled, so we cannot speak about the other points," he said.

Despite the agreement, heavy gunfire erupted around Donestk on Sunday , as clashes continue between both sides.

Lysenko said two soldiers had been killed over the past 24 hours, bringing the death toll since the original truce was declared to 37 servicemen and civilians.