BEIRUT – In one of the deadliest reported episodes of a nine-month uprising, Syrian security forces assaulting a village near the Turkish border surrounded and killed more than 100 people in a hail of tank and machine gun fire, opposition activists said Wednesday.

Tuesday’s attack on Kfar Owaid in the northwestern province of Idlib came as government forces pressed an offensive against a mountainous region where there have been weeks of protests and fierce clashes with military defectors fighting under the banner of the Free Syrian Army.

Opposition activists inside and outside Syria accused the government of trying to crush resistance to President Bashar Assad’s government before the arrival today of an advance team of Arab observers to monitor implementation of a regional peace initiative.

Journalists are heavily restricted in Syria and it was not possible to independently verify the activists’ accounts. The government did not immediately respond to the accusations. Officials deny that security forces are attacking unarmed civilians, blaming the bloodshed on what they describe as armed terrorist gangs, incited and supported from abroad. Government supporters rallied Wednesday in Damascus, the Syrian capital.

The Jabal Zawiyah mountains are a haven for the Free Syrian Army, whose leadership is based on the other side of the border in Turkey. Activists reached in Idlib province said a large government force moved into the region over the weekend and started attacking villages that had been providing refuge and support to the insurgents.

As many as 86 army conscripts tried to defect Monday and were killed in heavy shelling that also claimed the lives of 12 civilians in the village of Kansafra, said Mousab Azzawi of the British-based Syrian Observatory for Human Rights.

Others were surrounded and shelled in the forest north of the village as they tried to flee, he said citing witness accounts. The Observatory for Human Rights put the death toll from the village at 111 but activists in the region said it could be higher. Azzawi said activists had the names of 56 of the dead.

“This is some kind of collective punishment toward the local people,” Azzawi said.

The Syrian National Council, the country’s most prominent opposition bloc, called on the Arab League and United Nations to protect civilians, saying nearly 250 people were killed in “bloody massacres” across the country in the 48 hours ending Tuesday.

The council is pressing for the creation of safe zones, enforced by the international community, to protect civilians and insurgents fighting against Assad’s forces.

Under international pressure, Syria on Monday said it would admit observers to monitor an Arab League-negotiated peace plan calling for the withdrawal of security forces from urban areas and dialogue with the opposition. But opposition activists dismissed the move as a ploy to avoid wider international involvement.

The league had threatened to ask the U.N. Security Council to intercede if Syria did not sign a protocol for the observer mission.