Syria is denying reports that Vice President Farouq al-Shara has defected.
Syrian state television Saturday quoted a statement from Shara's office as saying the 73-year-old Sunni Muslim "never thought for a moment about leaving the country."
The channel also said Shara welcomed the U.N. appointment Friday of veteran Algerian diplomat Lakhdar Brahimi as international envoy to Syria.
Brahimi is replacing former U.N. secretary-general Kofi Annan, who will step down as envoy to Syria at the end of the month.
A U.S. spokesman said he could not confirm the reports of Shara's defection. But the spokesman said the regime of Syrian President Bashar al-Assad is becoming increasingly isolated.
In violence Saturday, Syrian activists said the military carried out air raids on rebel-held areas in the country, including the border town of Azaz in the northern region of Aleppo.
More than 40 people were killed in an attack on Azaz a few days ago.
On Friday, thousands of Syrians took to the streets in anti-government demonstrations, as Syrian aerial forces targeted opposition hubs in Aleppo and fought rebels in neighborhoods around Damascus.
The U.N. Security Council has said it is allowing the mandate for the U.N. observer mission in Syria to expire. The mandate ends Sunday, but the council said it hopes to establish a political office in the battle-ravaged country.
Some information for this report was provided by AP, AFP and Reuters.