Activists say fighting is raging in the southern suburbs of the Syrian capital and near the Damascus airport.
The Britain-based Syrian Observatory for Human Rights says Tuesday's clashes between rebels and troops loyal to President Bashar Assad are taking place in Beit Saham, Akraba and Yalda suburbs, as well as near the capital's international airport.
The Observatory relies on reports from activists on the ground.
The Damascus suburbs have been opposition strongholds since the uprising against Assad began in March 2011.
In the past weeks, the army has pressed an offensive to regain lost territory near the capital as the rebels push their way into Damascus, the center of Assad's power base.