Hundreds of army defectors in southern Syria fought loyalist forces backed by tanks on Sunday in one of the biggest armed confrontations in a nine-month uprising against President Bashar al-Assad, residents and activists said.

Troops, mainly from the 12th Armoured Brigade, based in Isra, 40-km (25 miles) from the border with Jordan, stormed the nearby town of Busra al-Harir.

The sound of explosions and heavy machineguns was heard in Busra al-Harir and in Lujah, an area of rocky hills north of the town, where defectors have been hiding and attacking military supply lines, they said.

Lujah has been the safest area for defectors to hide because it is difficult for tanks and infantry to infiltrate. The region has caves and secret passage ways and extends all the way to Damascus countryside, one of the activists, who gave his name as Abu Omar, said from the town of Isra.

(Reporting by Khaled Yacoub Oweis and Suleiman al-Khalidi, Amman newsroom)