British Prime Minister David Cameron urged Russia and China on Thursday to join the international community and help "tighten the noose" on the Syrian regime over its deadly crackdown on protests.

A U.N.-backed ceasefire to end 13 months of bloodshed in Syria appeared to be holding after coming into force at daybreak, but doubts remained about the compliance of President Bashar Assad's government with the peace plan.

German Foreign Minister Guido Westerwelle Wednesday pressed Russia to distance itself from Syrian President Bashar al-Assad's deadly crackdown on opposition rebels.

"Russia has to make clear that it does not want to have anything to do with these acts of violence and this repression," Westerwelle said on the sidelines of a two-day meeting with Group of Eight ministers in Washington.

Deputies from the opposition A Just Russia party staged a highly unusual walkout of the Russian parliament on Wednesday during an appearance by president-elect Vladimir Putin.

Faction leader Sergei Mironov led his deputies out of the chamber in protest at Putin's response to a question about a mayoral vote in the southern city of Astrakhan that his party says was rigged and prompted the local candidate to go on hunger strike.

Iran is to present "new initiatives" at nuclear talks with world powers in Istanbul on the weekend, the official leading the country's negotiating team, Saeed Jalili, said on Wednesday.

"The Iranian delegation will have new initiatives and we hope that the other party will have a constructive approach," he told Iran's Arab-language network al-Alam, without elaborating.

Prime Minister Vladimir Putin said on Wednesday Russia has beaten the economic crisis and called on political forces to unite as he prepares to return to the Kremlin next month.

Putin said in a keynote speech to the State Duma lower house of parliament that the 2008-2009 economic crisis was so serious it could have endangered Russia's sovereignty but added that the country had now fully recovered.

U.S. Secretary of State Hillary Clinton said Tuesday she would tell Russia that the risk of civil war was rising in Syria, adding that she expected "rough" diplomacy ahead.

Clinton said she would raise the Syria crisis when she meets Foreign Minister Sergei Lavrov in talks among foreign ministers of the Group of Eight major economies starting in Washington on Wednesday.

Syrian forces on Tuesday pounded protest hubs in apparent breach of a ceasefire deal brokered by U.N.-Arab League envoy Kofi Annan, who appealed for his plan to be implemented without preconditions.

Syria said it was abiding by the plan, but Annan accused Damascus of pulling troops from some areas and moving them to others, and the rebel Free Syrian Army warned it would resume attacks if the government offensive does not stop.

Syria's foreign minister told Moscow Tuesday Damascus has started withdrawing troops in line with Kofi Annan's peace plan but Russia said the regime should implement the initiative more decisively.

The rare visit by the veteran Foreign Minister Walid Muallem to Moscow coincided with a deadline under the Annan plan for Syria to withdraw forces from protest cities amid Western worries the scheme is in tatters.

Iran on Monday urged "honesty" at crucial talks with world powers due to be held this week in order to defuse a tense international showdown over its disputed nuclear activities.

"We hope the P5+1 will come to the negotiating table with honesty, and we also will make an honest effort so that both sides reach a win-win conclusion," Foreign Minister Ali Akbar Salehi told the Iranian parliament's website.

World powers will hold a fresh round of nuclear talks with Iran in Istanbul on April 14, a spokesman for European Union foreign policy chief Catherine Ashton said Monday.

"We have agreed to launch talks in Istanbul on April 14," Michael Mann said.