Activists say Syrian rebels have launched a counteroffensive in the northern city of Aleppo and recaptured a base near its international airport.

The Britain-based Syrian Observatory for Human Rights and the Aleppo Media Center say the rebels were able to fully recapture the site, the base for a unit called "Brigade 80," after government troops seized parts of it early Friday.

The main job of "Brigade 80" was to protect the government-held Aleppo International Airport, which has been closed due to fighting for almost a year.

Rebels captured the "Brigade 80" site in February and now government troops are trying to get it back.

The Observatory said 40 rebels and more than 20 troops were killed in the latest fighting, that began Friday and continued early Saturday.