Syrian President Bashar al-Assad's forces pounded resistance strongholds Saturday, the opposition said, raising questions about what immediate effect a plan by world powers to end the violence will have in the hardest-hit areas.

At least 33 people were killed Saturday across Syria, according to the Local Coordination Committees of Syria, a network of opposition groups. Casualties included 17 people killed in the besieged city of Homs, the group said. The city at the center of resistance has endured more than three weeks of daily shelling.

Reports of renewed violence followed news Friday that dozens of countries agreed to increase pressure on al-Assad while laying groundwork for a political transition in Syria not unlike the international planning that preceded the fall of Libyan ruler Moammar Gadhafi last year.