The opposition Syrian National Council is calling for a general strike on Thursday to protest what it says is a brutal government crackdown in the central Homs region.
Activists say security forces have carried out a series of raids in Homs over the past week that have left dozens of people dead.
They blame security forces for more than 110 deaths since the Syrian government agreed last week to an Arab League plan that calls for an end to violence. Under the agreement, Damascus promised to withdraw its security forces from the streets and begin talks with the opposition.
The Arab League will meet on Saturday to discuss a possible response to Syria's broken pledge to end the brutal crackdown on dissent.
Pressure is building for the league to move decisively against President Bashar al-Assad's government. In a briefing Wednesday, U.N. human rights chief Navi Pillay said Syria faced a serious risk of descending into an armed struggle similar to the one Libya experienced.
She welcomed the commitments Syria made to the Arab League but voiced concern that civilian killings have not stopped.
Also Wednesday, U.S. Assistant Secretary of State for Near Eastern Affairs Jeffrey Feltman urged the league to take a tougher stance against Damascus as part of a global effort to force Assad from power.
Activists said 24 people were killed in unrest across Syria on Wednesday. The causality figure could not be independently verified because Syria bars most foreign journalists from operating in the country.
Earlier this week, the U.N. human rights office says at least 3,500 people have been killed in the country since the anti-government uprising began in March.
Some information for this report was provided by AFP and Reuters.