U.S. Secretary of State John Kerry arrived in Moscow Tuesday for talks with Russian President Vladimir Putin, seeking to restore frayed U.S.-Russia ties and win Moscow's support on the war in Syria.

Kerry is making his first trip to Russia since taking over as the chief U.S. diplomat in February, on what is one of his most diplomatically delicate missions to date.

U.S. Secretary of State John Kerry set off for Russia on his first visit since taking up the post on Monday, traveling with a diplomatic bag bulging with global problems, including the war in Syria.

In a rare break with protocol he was to meet with Russian President Vladimir Putin on Tuesday, for what a senior State Department official called "a fantastic opportunity" for talks on the entire bilateral relationship.

Thousands of protesters on Monday filled a square in central Moscow to denounce Russian President Vladimir Putin one year into his new Kremlin term, as the opposition seeks to recover the momentum of their challenge to his rule.

Organizers said tens of thousands attended the rally, which marks one year since a chaotic May 6, 2012 anti-Kremlin protest that descended into violence, and Putin's return to the presidency a day later. Police estimated the numbers at 7,000.

Russian President Vladimir Putin held telephone talks with Israeli Prime Minister Benjamin Netanyahu over the Syrian conflict, the Kremlin said Monday, after Israel launched air strikes inside Syria.

Putin and Netanyahu discussed the "situation in the region and the situation around Syria," the president's spokesman Dmitry Peskov said in a statement to Russian news agencies, without giving further details. The Russian foreign ministry had earlier expressed concern over the air strikes.

A Russian helicopter carrying nine people including senior rescue service officials as well as almost two tonnes of explosives has crashed in the Irkutsk region of southern Siberia, regional officials said Monday.

"The remains of the missing helicopter were found at 1930 local time (1030 GMT) six kilometers from the village of Preobrazhenka," the Irkutsk regional emergency situations ministry said in a statement.

About a thousand Muscovites rallied Sunday in memory of a bloody protest one year ago in which more than 400 were detained after showing their frustration with Vladimir Putin's return to the presidency.

The "Spring March of Freedom" was held almost a year to the day since Russian authorities deployed baton-wielding interior ministry troops to disperse a crowd of tens of thousands on the eve of Putin's May 7 swearing-in ceremony.

The U.N. Security Council is not entitled to give the green light for inspections of Syrian refugee camps in Jordan, Russian Foreign Minister Sergei Lavrov said Friday, seeing it as an attempt to prepare "foreign intervention".

The U.N. High Commissioner for Refugees (UNHCR) "is competent for (organizing) visits of refugee camps that have been set by the U.N., the Security Council has no competence for that," Lavrov said in Slovenia.

A majority of U.N. Security Council members support a trip to inspect Syrian refugee camps inside Jordan but Russia and China remain opposed to a visit, diplomats said Thursday.

Jordan this week warned that the growing exodus of Syrian refugees who had flooded over its border to escape civil war -- already over 500,000 -- was placing a "crushing weight" on the country.

President Vladimir Putin on Wednesday handed out the first "Hero of Labor" awards to Russians since reviving the Soviet-era tradition this year, with recipients ranging from top conductor Valery Gergiev to a Siberian coalminer.

The honorary Hero of Labor award and medal, recreated by the Kremlin in March for the first time since the end of the Soviet Union, was bestowed on a group of five people for the first time as Russia marked the May 1 holiday with organized parades of labor unions and pro-Kremlin politicians.

Three police officers were killed and two more injured when gunmen opened fire on their cars in Russia's restive region of Dagestan, investigators said Wednesday.

A police major and two other officers were killed on Tuesday evening while driving through Buinaksk, a city about 30 kilometers (18 miles) from the capital of Dagestan, Makhachkala, in Russia's North Caucasus.