China said Thursday it had made "constructive new suggestions" to end the bloodshed in Syria, including a phased region-by-region ceasefire and the formation of a transitional government.

In an apparent attempt to position China at the heart of efforts to solve the issue, the foreign ministry gave a detailed account of proposals it made to Lakhdar Brahimi, the visiting United Nations-Arab League joint peace envoy.

Syria's conflict is going from bad to worse, the U.N.-Arab League peace envoy said Monday after key talks in Moscow on finding a solution, expressing disappointment that his four-day truce plan had failed.

"I have said and it bears repeating again and again that the Syrian crisis is very very dangerous, the situation is bad and getting worse," envoy Lakhdar Brahimi said after talks with Russian Foreign Minister Sergei Lavrov.

A cargo ship with 11 crew on board went missing Sunday in Russia's Far East in stormy conditions that were making rescue operations difficult, an emergency ministry spokeswoman said.

The "Amurskoye" was traveling to the Shantar Islands in the icy Okhotsk Sea, which lies east of Russia's Khabarovsk region and north of Japan's Hokkaido island.

Russian police detained several opposition leaders, including Alexei Navalny and Sergei Udaltsov, during a protest staged by about 200 people in central Moscow on Saturday, they said on Twitter.

"I was walking on the sidewalk. They detained me without any explanation," Left Front movement leader Udaltsov, one of the prominent organizers of mass protests against President Vladimir Putin, said on his Twitter account.

Ukraine's security service said Friday it was conducting a formal check into the disappearance of a Russian opposition activist who claimed to have been abducted from Ukraine by Russian agents.

The Security Service of Ukraine (SBU) said in a statement that it was looking into the "urgent departure" of Leonid Razvozzhayev, who is now in a Moscow prison after being charged with plotting mass riots.

Vladimir Putin's Kremlin has carefully avoided taking sides in the U.S. presidential race with a victory by either Barack Obama or Mitt Romney offering potential strategic pluses for the Russian strongman.

Obama spearheaded the "reset" to improve ties which hit a Cold War-style freeze when he took on the presidency and his exit from the White House would dampen hopes of greater military, diplomatic and economic cooperation.

Russia on Friday charged protest leader Sergei Udaltsov with plotting mass riots in a controversial probe that has seen the detention of another activist who claims to have been tortured into confessing.

Udaltsov was charged after being summoned by the Investigative Committee for questioning over an alleged plot to hold mass riots with international funding to topple President Vladimir Putin.

Russia accused Washington on Thursday of "coordinating" deliveries of arms to Syrian rebels, despite assurances by the State Department that the United States provides no lethal assistance.

"Washington is aware of the deliveries of various weapons to illegal armed groups active in Syria. Moreover, judging by the declarations of U.S. officials published in U.S. media, the U.S. coordinates and provides logistical assistance in such deliveries," the foreign ministry said in a statement.

The Syrian rebels battling the regime of President Bashar Assad have shoulder-launched missile systems, including Stingers made by the United States, Russia's top general said on Wednesday.

Russian chief of staff General Nikolai Makarov, whose country is the Syrian regime's top arms supplier and has refused to back the rebels, said it was not clear who had delivered the weapons.

Iran could soon host a "national dialogue" in the region between all the parties to the Syrian conflict, a senior Iranian official said in media reports on Tuesday.

"Representatives of the (Syrian) government and all political and opposition groups will soon begin a national dialogue in a regional country, and possibly in Tehran," said Hossein Amir Abdollahian, deputy foreign minister for Arab affairs, quoted by the official IRNA news agency.