The deputy chief of the Arab League says his organization has halted its observer mission in Syria because of the increasing violence there.

Deputy Secretary General Ahmed Ben Heli says the observers who are still in Syria, numbering around 100, have stopped their work after a decision by member states because of the sharp spike of bloodshed in recent days. He says the observers are staying in their Damascus hotel until further notice.

Meanwhile, Syrian forces killed at least 12 people on Saturday and injured 30 in a bombardment of suburbs of Damascus that have fallen under rebel control, activists said. About half of those killed were civilians. The rest were army defectors loosely grouped under the Free Syrian Army, they said.

Most casualties were from anti-aircraft gunfire and mortar rounds that hit the suburbs of Saqba, Hammouria and Kfar Batna on the eastern edge of the Syrian capital, they added.

Arab League chief Nabil Elaraby and the prime minister of Qatar are heading to New York on Saturday to seek UN support for an Arab plan to end Syria's crisis.

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In this image from amateur video shot on Dec. 30, 2011, Arab League observers are seen at a protest in Idlib, Syria. (Shaam News Network via APTN/AP )

The decision to suspend the mission was announced earlier Saturday, about a week after the league decided to extend its mission for an extra month.

Intense fighting has erupted between Syrian troops and anti-regime army defectors in the central province of Homs and suburbs of the capital Damascus, said opposition activists.

The British-based Syrian Observatory for Human Rights and the Local Co-ordination Committees also said Syrian security forces shelled the eastern town of Qoriah on Saturday, killing at least one person.

The groups said an oil pipeline took a direct hit and caught fire as government troops shelled the town, which is located in the oil-rich province of Deir el-Zour.

The Syrian uprising, which began last March with mostly peaceful protests, has become increasingly violent in recent months.

The United Nations estimates that more than 5,400 people have died in the turmoil.