COTABATO CITY, the Philippines - Philippine security forces have killed an Abu Sayyaf sub-leader in the restive south, a military official said Monday.

Government soldiers were on patrol mission around 7:00 pm Sunday when they encountered undermined number of Abu Sayyaf militants in Busay village, Zamboanga city, said Task Force Commander Col Buenaventura Pascual.

Pascual said a 20-minute gun battle ensued, resulting in the death of Imram Asgani, a sub-leader of the militant group.

"There were no casualties on the government side. Our men also recovered assorted ammunition left behind by the rebels," said Pascual.

The Abu Sayyaf, active in southern Philippines, was founded in the 1990s and has perpetrated a number of high-profile attacks, including kidnapping, bombing and beheading. The Philippine military estimates the Abu Sayyaf, which has links with external terrorist organizations such as al-Qaeda, currently has less than 400 members.