A U.N. commission of inquiry on Syria called Monday for direct access to the U.N. Security Council to make the case for referring crimes committed in the war-torn country to the International Criminal Court.

"We want access... directly to the Security Council and the General Assembly," said Vitit Muntarbhorn, one of the four investigators who make up the commission.

The Syrian regime appears to be using local militias known as Popular Committees to carry out sometimes sectarian mass-killings in Syria, a U.N. inquiry team said Monday.

"In a disturbing and dangerous trend, mass killings allegedly perpetrated by Popular Committees have at times taken on sectarian overtones," the U.N. commission of inquiry, led by Brazilian Paulo Pinheiro, said in an update to its latest report on Syria.

Turkish security forces arrested Monday four Syrians linked to President Bashar Assad's regime over a deadly bomb attack on the volatile border last month, the interior minister said.

"Our security forces arrested four Syrian nationals and one Turkish citizen" over the minibus bombing which killed 14 people, Muammer Guler said in televised remarks. "We proved their links with the Syrian intelligence and army."

Syrian jets Monday bombed Baba Amr in a bid to repulse a rebel attack on the strategic neighborhood of Homs city, a watchdog said, adding that street battles erupted intermittently during the night.

Rebels launched their assault on Baba Amr at dawn on Sunday, hoping to take back the neighborhood which they lost to President Bashar Assad's forces a year ago.

A top Syrian opposition official met Russia's Foreign Minister Sergei Lavrov on Monday in a bid to reverse Moscow's refusal to back calls on President Bashar Assad to step down.

Haytham Manna of the National Coordination Committee for Democratic Change -- Syria's second-largest anti-Assad group -- said he thought the road to peace in Syria ran through Moscow.

U.S. Deputy Assistant Secretary of State for Energy Diplomacy Amos Hochstein and Acting Deputy Assistant Secretary of State for Near Eastern Affairs Lawrence Silverman visited Lebanon Monday and met with senior officials to discuss the political, economic and security situation in Lebanon and other regional issues, said the U.S. Embassy in a statement.

They had meetings with President Michel Suleiman, Speaker Nabih Berri, Prime Minister Najib Miqati, and Minister of Energy Jebran Bassil.

Al-Qaida's Iraqi front group claimed an attack on a convoy in west Iraq that killed 48 Syrian soldiers and nine Iraqi guards, in a statement posted on jihadist forums on Monday.

The soldiers had entered Iraq for medical treatment and were being transported through the western province of Anbar on their way back to Syria when the attack took place on March 4, according to the Iraqi defence ministry.

Lebanese Forces leader Samir Geagea slammed on Monday allegations by Hizbullah that it is engaged in battles in the Syrian province of Aleppo so it wouldn't be forced to slip into fights in Lebanese territories.

“Hizbullah's meddling in Syria will attract the rebel Al-Nusra Front (a jihadist group involved in the conflict in Syria) to move the clashes into Lebanon,” Geagea told An Nahar newspaper.

Syria's National Coalition has for the second time in weeks postponed talks on the formation of an interim government, a senior member of the opposition grouping said Sunday, citing "deep rifts" on the issue.

The meeting was initially scheduled for last month in Istanbul but was postponed until Tuesday this week. It has now been delayed again, with a possible new date between March 18 and 20, said Samir Nashar.

The number of Syrian refugees, which just passed the million mark, could double or triple by the end of the year if no solution is found to the conflict, U.N. High Commissioner for Refugees Antonio Guterres said Sunday.

"Now if this escalation goes on and nothing happens to solve the problem we might have in the end of the year a much larger number of refugees: twice or three times the present level," he told reporters in Ankara.