Syria's military and security forces have committed crimes against humanity in their deadly crackdown on anti-regime protesters, U.N.-appointed investigators said on Monday.

State forces have murdered, raped and tortured demonstrators since the beginning of protests in March this year, according to evidence gathered by the Independent Commission of Inquiry on Syria.

U.S. Ambassador to Lebanon Maura Connelly expressed on Monday the United States’ concern over the possibility of Lebanon failing to meet its obligations to Special Tribunal for Lebanon.

She said after holding talks with Economy Minister Nicolas Nahhas: “Its failure to meet these obligations could lead to serious consequences.”

The European Union will tighten sanctions against Syria's oil and financial sectors this week to punish the regime over its crackdown on protesters, a European diplomat said Monday.

EU foreign ministers meeting Thursday will adopt a raft of sanctions including bans on exporting gas and oil industry equipment to Syria, trading Syrian government bonds and selling software that could be used to monitor Internet and telephone communications, the diplomat said.

Syria has withdrawn almost all of its assets from Arab countries, Foreign Minister Walid Muallem said Monday, a day after the Arab League slapped sanctions on Damascus for its refusal to halt a protest crackdown.

"I reassure you that we have withdrawn 95 or 96 percent of Syrian assets (from Arab countries)," Muallem told a news conference. "We must protect the interests of our people."

Syrian Foreign Minister Walid Muallem on Monday hit out at the Arab League for the treatment it has meted out to Damascus, accusing it of ignoring the presence of "terrorists" in the country and prematurely imposing economic sanctions.

Muallem made the accusation at a news conference at which gruesome video footage was shown of what was described as a "mass grave of security force martyrs" that the authorities had discovered.

Tens of thousands of Syrians demonstrated in the capital Monday against the Arab League decision to impose crippling sanctions on President Bashar Assad's regime, an Agence France Presse correspondent reported.

Protesters waved Syrian flags and carried giant portraits of the embattled leader as they belted nationalistic songs in Damascus' central Sabaa Bahrat square.

Russia will send a flotilla of warships led by its only aircraft carrier to its naval base in Syria for a port call next year amid tensions with the West over the Syrian crisis, a report said Monday.

The ships, headed by the Admiral Kuznetsov aircraft carrier, will dock at the little-utilized Russian base in the Syrian port of Tartous in spring 2012, the Izvestia daily said, quoting the Russian navy.

French Foreign Minister Alain Juppe said Monday that time was running out for the regime in Syria after the Arab League agreed sweeping sanctions against Damascus over its deadly crackdown on protesters.

"Its days are numbered, that is obvious. It is totally isolated today," Juppe told France Info radio, while acknowledging that efforts to try to stem the bloodshed in Syria were moving slowly.

French military forces are training armed Syrian rebels in Turkey and Lebanon to fight the government of Syrian President Bashar Assad, a Turkish newspaper has reported.

According to Milliyet, as cited by The Islamic Republic News Agency, IRNA, the French forces are training the so-called Free Syrian Army to wage war against Syria's military.

Turkey will support a raft of sanctions on neighbor Syria agreed by the Arab League at a meeting in Cairo, Foreign Minister Ahmet Davutoglu said Sunday.

"Turkey is supporting the decisions and measures taken by the Arab League against Syria," Davutoglu was quoted as saying by the Anatolia news agency on the sidelines of the Cairo meeting, to which non-Arab Turkey was invited.