China on Thursday backed U.S. President Barack Obama's calls for the U.S. and Russia to slash their atomic arsenals, saying the two former Cold War rivals should bear the brunt of global nuclear disarmament.

"The U.S. and Russia... should substantially reduce their nuclear arsenal in a verifiable and responsible manner," Foreign Ministry spokeswoman Hua Chunying said at a regular briefing in Beijing.

Russian security services sought Thursday to unravel a mystery after a fraudster managed to fool the country's news agencies into believing one of President Vladimir Putin's closest allies had been "fired" from his post.

The purported dismissal of Vladimir Yakunin as head of Russian Railways (RZD) was flashed by Russia's three main wires on Wednesday after they had received an emailed statement looking very much like an official government press release.

China and Russia on Thursday blasted a U.S. report that downgraded their countries for failing to make greater efforts to combat human trafficking, a move which could lead to sanctions.

"We believe that the U.S. side should take an objective and impartial view of China's efforts (in fighting human trafficking) and stop making unilateral or arbitrary judgments of China," foreign ministry spokeswoman Hua Chunying said at a regular briefing in Beijing.

Russia said on Thursday the West did not want to commit to a concrete timeframe for a proposed peace conference on Syria because it was not sure the opposition would agree to attend.

In May, Russia and the United States proposed putting together a peace conference in a bid to try to find an end to the civil war in Syria but the date for the talks has repeatedly been pushed back.

President Barack Obama said Russian and U.S. nuclear weapons should be slashed by up to a third in a keynote speech in front of Berlin's iconic Brandenburg Gate in which he called for a world of "peace and justice".

Obama used the once divided city's rebirth as a metaphor for progress, as he stood on the east side of the route of the Berlin Wall, and warned the "complacent" West that history did not stop with its Cold War victory.

More than six thousand people were evacuated overnight in central Russia after a series of massive explosions at an arms depot blew out windows and sparked a fire, the emergency situations ministry said Wednesday.

The blasts began Tuesday night and continued for hours after being sparked by efforts to dispose of munitions at an arms depot close to the town of Chapayevsk in the Samara region around 1,000 kilometers (620 miles) from Moscow.

U.S. President Barack Obama will on Wednesday propose the United States and Russia cut strategic nuclear warheads by a third and reduce tactical nuclear arsenals in Europe, a U.S. official said.

Obama, who will make the proposals in a major speech in Berlin, will also commit to attending a nuclear security summit in The Hague next year, and to holding a similar meeting in the final year of his presidency in 2016.

President Vladimir Putin said Tuesday that Russia would not rule out sending fresh arms to the Syrian regime and warned the West against arming "criminals" in the rebellion.

"If we conclude such contracts, then we will deliver on such contracts," he told reporters after a G8 summit in Northern Ireland.

Russia believes it is time to consider relaxing sanctions pressure on Iran amid hope of progress in the standoff over its nuclear program, Foreign Minister Sergei Lavrov was quoted as saying Tuesday.

"It is necessary to avoid tightening the sanctions pressure against Tehran and start thinking about ways for a possible weakening (of sanctions) in a way that is tangible for Iran," Lavrov said in an interview with Kuwaiti news agency KUNA

The planned peace conference in Geneva to end the conflict in Syria should not imply any capitulation on the part of the regime of Syrian President Bashar Assad, Russian Foreign Minister Sergei Lavrov was quoted as saying Tuesday.

"We are categorically against... assertions that the conference should be some kind of public act of capitulation by the government delegation followed by a handing over of power to the opposition," Lavrov told Kuwaiti news agency KUNA in an interview whose text was published by the Russian foreign ministry.