DAMASCUS - Rebels backed by Syria's Al-Qaeda affiliate seized control Wednesday of the last border crossing with Jordan that had been under regime control, dealing a major blow to President Bashar al-Assad.
"Armed groups, joined today by Al-Qaeda affiliate Al-Nusra Front, took over the Nasib border point from regime soldiers" on the Syrian side of the frontier, said Rami Abdel Rahman of the Syrian Observatory for Human Rights.
A coalition of rebel groups had launched the offensive Tuesday, and Al-Nusra joined them late Wednesday.
A pro-regime security source said the "Syrian army withdrew from the Nasib border crossing." Abdel Rahman said the takeover meant there was "no longer a regime presence on the border with Jordan."
Shortly afterwards, regime helicopters began dropping barrel bombs - crude weapons made of oil drums or barrels stuffed with explosives - on rebel positions near Nasib, said the Observatory director.
There was no immediate information on any casualties.
Jordan had said earlier it closed the crossing, which leads to Syria's Daraa province, to both travellers and goods.
It was a "preventive measure to safeguard the lives and security of travellers due to the fighting underway on the other side of the border," Interior Minister Hussein Majali told AFP.
Rebels have been gaining territory in the southern province of Daraa, cradle of the 2011 Arab Spring-inspired uprising against Assad that triggered Syria's civil war.
Last week they seized full control of the ancient town of Bosra al-Sham, pushing pro-regime forces out after days of heavy fighting.
In January rebels - including Al-Nusra Front - seized an important government army base in the province.
IS's first Damascus foray
In another upset for the regime, the extremist Islamic State group stormed a refugee camp in Damascus its first assault inside the capital.
Clashes between armed factions and IS jihadists raged in the Yarmuk refugee camp in southern Damascus after the jihadists overran much of the Palestinian haven in a lightening assault.
"Fighters from IS launched an assault this morning on Yarmuk and they took over the majority of the camp," said Anwar Abdel Hadi, the Palestine Liberation Organisation's political affairs director in Damascus.