Syrian forces killed at least three people in Homs early Friday, as opposition leaders called for mass protests to test the government's commitment to a new peace plan.

Activists say the three civilians died after Syrian forces in tanks renewed artillery fire in the flashpoint Baba Amr district of Homs. On Thursday, activists blamed pro-government forces for at least 12 deaths in the city.

Meanwhile, the Local Coordination Committees urged opponents of President Bashar al-Assad to take to the streets after Friday prayers with new calls for his departure.

On Wednesday, the Arab League brokered a plan to halt violence and convene talks between the government and the opposition. However, Thursday's deaths and military action cast doubt on a quick implementation of the plan.

In Cairo Thursday, members of the opposition Syrian National Council met with the Arab League chief to discuss the way forward.

Council member Samir al-Nashar said the group did not discuss possible dialogue with the Syrian government but instead asked that Mr. Assad step down. The SNC then offered to “engage in negotiations” to move from an authoritarian government to a democratic one.

The United Nations says the number of people killed during the eight-month-old uprising against Mr. Assad has topped 3,000.

The Syrian government has blamed much of the unrest — including deadly violence in Homs this week — on “terrorists” and gunmen.