Government troops have repulsed a rebel attack on a police school in the northern city of Aleppo, killing and wounding opposition fighters.
The incident comes the day after a rare public speech by President Bashar Assad, in which he called on Syrians to fight rebels who he characterised as religious extremists.
State news agencies did not specify the number of casualties reportedly inflicted on the "terrorist group", the pro-regime media's usual term for the rebels.
The rebels have recently made significant advances, capturing air bases and military installations in the east and around Damascus, the seat of Assad's power.
In his speech, Assad laid out terms for a peace plan but dismissed any chance of dialogue with "murderous criminals".
Assad appeared confident and relaxed in a one-hour speech - his first public address in six months. He struck a defiant tone, ignoring international demands for him to step down and saying he is ready to hold a dialogue - but only with those "who have not betrayed Syria." He also vowed to continue the battle "as long as there is one terrorist left."
He offered a national reconciliation conference, elections and a new constitution but demanded regional and Western countries stop funding and arming rebels trying to overthrow his regime first.
Syria's opposition swiftly rejected the proposal. Those fighting to topple the regime, including rebels on the ground, have repeatedly said they will accept nothing less than the president's departure, dismissing any kind of settlement that leaves him in the picture.