Rebels seized a military airport in Syria's northern province of Aleppo on Tuesday, killing, injuring and capturing a total of around 40 troops, said the Syrian Observatory for Human Rights.
"The remainder of the troops pulled out from the airport, leaving behind several warplanes and large amounts of ammunition," Observatory director Rami Abdel Rahman told AFP.
The capture of the Al-Jirah military airport came a day after Islamist rebels overran the town of Tabqa, situated in the neighbouring province of Raqa, before taking control of the nearby strategic Al-Thawra dam on the Euphrates.
"The rebels' progress in this area has been extremely quick," said Abdel Rahman.
"While the army has full control of parts of Damascus province, the capital and the central province of Hama, it is suffering losses in Homs in the centre, Deir Ezzor in the east, and Aleppo and Raqa in the north," he added.
"There are clashes all over the country, and it is impossible for the army to control every flashpoint."
Activists in Aleppo have told AFP rebel fighters in the north have shifted their focus in recent weeks to the capture of military airports and bases.
"They are important because they are an instant source of ammunition and supplies, and because their capture means putting out of action the warplanes used to bombard us," Aleppo-based activist Abu Hisham told AFP via the Internet.