Updated

Fighters from Lebanon's Hezbollah joined Syrian troops battling rebels near Damascus on Wednesday, monitors said, as President Bashar al-Assad's regime kept up a push to cut off the insurgents' supply lines.

"Army troops and Hezbollah members fought rebels near the Khomeini hospital in Zayabiyeh village," southeast of Damascus, said the Syrian Observatory for Human Rights.

"Hezbollah fighters, who have a strong presence at Sayyida Zeinab (in southeastern Damascus), are trying to seize control of villages near Zayabiyeh and Babila."

The Syrian army shelled both Zayabiyeh and Babila, said the group which relies on a network of activists, doctors and lawyers on the ground for its reports.

Hezbollah's Al-Manar television said the army was advancing towards Zayabiyeh, just south of the confessionally mixed district of Sayyida Zeinab, named after an important Shiite Muslim shrine.

The Lebanese Shiite movement has been fighting alongside the army for months in the district, which lies in an area that rebels from southern Damascus have used as their main rear base.

Activists say the regime is trying to crush the rebellion on the outskirts of Damascus in order to cut off supply lines leading into rebel pockets inside the capital.

"There is a fierce campaign against the (rebels) south of the capital," said Damascus-based activist Matar Ismail.

"The humanitarian situation is very critical... We believe the (regime) is trying to test the (rebels') strength, in order to try to advance on the south of the capital," Ismail told AFP over the Internet.

Ismail said Hezbollah and the Abu al-Fadl Abbas brigade -- a mostly Syrian Shiite force that has also attracted Shiite fighters from elsewhere in the region -- were playing a key role in the fight.

Hezbollah was also credited with an important role in the Syrian army's recapture of the former rebel stronghold of Qusayr in central Homs province earlier this month.

The leader of Hezbollah, Hassan Nasrallah, has said the Lebanese group will remain engaged in Syria's conflict.

The Syrian army meanwhile renewed shelling of other rebel areas near the capital, including northwestern Zabadani and Qalamoun to the northeast.

Both areas are also a short distance from the Lebanese border.

Elsewhere, fierce battles broke out between rebels and troops in Idlib, in northwestern Syria, the Observatory said.

Opposition forces captured an army post on the road linking the coastal province of Latakia to Ariha in Idlib province, and two tanks were destroyed.

In regime stronghold Latakia, an explosion at an ammunition depot wounded at least 13 soldiers, said the Observatory.

State television said the blast was the result of a technical failure, and that only six had suffered light wounds.

Wednesday's violence comes a day after at least 83 people were killed across Syria, said the Britain-based Observatory.