BEIRUT: Syrian rebels Thursday launched an assault on Wadi Daif, one of the last military bases in northwestern Syria still under the regime's control, while fighting also erupted around Damascus, a watchdog said.

Several rebel brigades joined forces for the attack on the fortress-like base in Idlib province, while the army responded with heavy fire and shelling, the Syrian Observatory for Human Rights (SOHR) said.

Further south, rockets struck areas between Al-Hajar al-Aswad and the Palestinian refugee camp of Yarmuk in Damascus province, the Britain-based Observatory said.

It added that warplanes bombed orchards in a rebel-held zone extending from Kfar Sousa near Damascus to Daraya in the southwest, where fighting has been raging for weeks.

In video footage the rebels announced on Wednesday they are holding the representative of the interior ministry for the town of Daraya, the de facto local head of police.

Elsewhere, a rebel was killed in clashes in the city of Deir Ezzor in the east, while another was killed in a village near the central city of Homs, said the Observatory which relies on a network of activists and medics on the ground.

On Wednesday, at least 158 people were killed in Syria, including 99 civilians, the Observatory said in its daily toll.

The watchdog has recorded more than 40,000 people killed since a popular uprising against the regime of President Bashar al-Assad broke out in March last year.