Activists say opposition fighters are clashing with Syrian government forces in the capital Damascus for a second day.
Activists and residents say the fighting in several neighborhoods is among the heaviest since the uprising against President Bashar Assad's regime began in March last year.
The Britain-based Syrian Observatory for Human Rights and Syria-based activist Mustafa Osso say Monday's clashes concentrated in the districts of Kfar Souseh and Tadamon.
A resident who spoke on condition of anonymity for fear of reprisals says gunfire and sporadic explosions could be heard Monday morning.
Damascus is tightly controlled by Assad's forces, although there have been sporadic clashes in the capital in recent months.
The fighting comes as U.N. special envoy Kofi Annan will visit Moscow to discuss the Syrian crisis with Russian leaders.
