British Prime Minister David Cameron has urged President Vladimir Putin to ensure fair treatment for crew members of a Greenpeace ship held in Russia, his office said on Wednesday.

The Russian leader was "understanding" of the concerns expressed by Cameron in a phone call on Tuesday, said a spokeswoman for the prime minister's Downing Street office.

Russian opposition leader Alexei Navalny has thrown his weight behind a controversial nationalist march in Moscow as rights activists warn of growing xenophobia in the country.

The top critic of President Vladimir Putin is known for his ability to mobilize mass street protests, although he said he himself would have to skip Monday's Russian March.

Japan and Russia took a step towards making a peace that has eluded them since World War II on Friday, with a loose agreement for talks on a treaty.

Japanese Foreign Minister Fumio Kishida and his Russian counterpart Sergei Lavrov agreed there would be negotiations aimed at settling the dispute, which centers around the sovereignty of a chain of islands north of the Japanese island of Hokkaido.

Having outfoxed him on Syria, Russian President Vladimir Putin has pipped Barack Obama to the title of the world's most powerful leader as ranked by Forbes on Wednesday.

It was the first time in three years that the U.S. president has dropped to second place on the magazine's list and came as U.S.-Russia relations slid to a new low.

Several thousand Russians marched through central Moscow on Sunday in a new protest at President Vladimir Putin's rule and a judicial crackdown against opponents.

Chanting "Putin is a thief" and "Freedom to political prisoners!", protesters marched with flags and portraits of people seen as victims of political persecution, such as jailed former oil tycoon Mikhail Khodorkovsky, members of punk band Pussy Riot, and the Greenpeace Arctic crew.

Russian President Vladimir Putin on Tuesday accused foreign "forces" of using radical Islam to sow discord in Russia, after a Muslim suicide bomber killed six on a bus in southern Russia.

"Some political forces are using Islam or more precisely its radical strains...to weaken our state, to create in Russia zones of 'ethnic conflict ruled from outside,' to drive a wedge between different ethnic groups, inside the Muslim community, to inflame separatist sentiments in provinces," Putin said, without providing specifics.

Indian Prime Minister Manmohan Singh met Russian President Vladimir Putin on Monday amid signs that the two giants had failed to reach a breakthrough on a long-delayed nuclear power deal.

Singh is using one of his last major foreign trips as prime minister before 2014 general elections to seek resolutions to lingering issues with two of India's most important regional partners.

A Russian embassy flat in The Hague was broken into on Thursday night, the latest incident to spike tensions between the two countries which Dutch police said appeared to be a regular burglary.

"Some personal effects were stolen, I can't say what," police spokeswoman Ellen van Zijl told Agence France Presse on Friday, adding that no arrests had yet been made over the break-in at a house located close to the Russian embassy grounds.

German Chancellor Angela Merkel voiced concern Wednesday to Russian President Vladimir Putin over the detention of 30 Greenpeace members who had protested Arctic drilling.

The environmental activists have been held on piracy charges in the northern region of Murmansk for almost three weeks after their ship Arctic Sunrise was seized by Russian security forces in a commando-style operation.

In perhaps an unprecedented burst of birthday diplomacy, Russian President Vladimir Putin celebrated turning 61 by quaffing vodka, wolfing down cake and being serenaded by some of the world's most powerful men.

Putin Tuesday recounted a series of light-hearted birthday moments that livened up the normally dour conference halls of a trade-focused Asia-Pacific leaders' summit on the Indonesian resort island of Bali.