President Vladimir Putin vowed on Tuesday not to let Russia be weakened by social shocks as tens of thousands of demonstrators gathered in Moscow to protest his historic third term.

"We cannot accept anything that weakens our country or divides society," he said in a televised address on the Russia Day national holiday.

Tens of thousands of protesters chanting "Russia Will be Free" rallied in Moscow on Tuesday against President Vladimir Putin's third term despite a police crackdown on their leaders a day earlier.

Flag-waving crowds made their way down leafy boulevards from Moscow's central Pushkin Square as the march began with police putting the numbers at around 18,000.

Russia's President Vladimir Putin on Friday said he had signed a controversial bill that sharply raises fines for opposition protesters despite pleas from rights activists to veto the law.

Russian President Vladimir Putin told his Iranian counterpart on Thursday that Moscow supports Tehran's atomic program as long as it is "peaceful".

"We have always supported the right of the Iranian people to modern technologies, including the peaceful use of atomic energy," he told Mahmoud Ahmadinejad on the sidelines of a regional security summit in Beijing.

Russia and China strongly oppose foreign military intervention in Syria or Iran, said a joint statement released on Wednesday after Russian President Vladimir Putin met with Chinese leaders.

"Russia and China are decisively against attempts to regulate the Syrian crisis with outside military intervention, as well as imposing a policy of regime change, including within the Security Council," the statement said.

Russian President Vladimir Putin started a visit to China Tuesday aimed at bolstering a crucial alliance, with foreign policy to the fore as the neighbors seek to block action against Syria.

Putin will also meet the presidents of Iran and Afghanistan as part of a regional summit during the three-day visit, his first to Asia since starting an historic third term last month.

Russia and the European Union must overcome their differences on the crisis in Syria to prevent a full-scale civil war, the EU president said Monday after talks with Russian President Vladimir Putin.

Herman Van Rompuy, who is in Russia with EU Commission chief Jose Manuel Barroso to meet with Putin, admitted after the talks that the EU and Russia "might have some divergent assessments" over the situation in Syria.

French President Francois Hollande said Friday that no solution is possible in Syria without "the departure of Bashar Assad.”

He spoke at a press conference with Russia's Vladimir Putin.

Germany and Russia agreed on the need for a political solution to end the bloodshed in Syria, their leaders said after talks here Friday, as Vladimir Putin warned the country could be on the brink of civil war.

The Russian president said the situation in strife-wracked Syria was "extremely dangerous" but underlined his opposition to military intervention, after meeting German Chancellor Angela Merkel on the second leg of his first foreign tour since returning to the Kremlin.

U.S. Secretary of State Hillary Clinton met with Norwegian officials Friday as she toured Scandinavia to praise the work of key U.S. partners in a range of global hotspots.