MANILA - The Philippines security forces killed 11 Muslim militants in clashes in southern Sulu province, stronghold of the small but brutal Abu Sayyaf extremist group.

Three special forces soldiers died, and 17 others were injured, the military reported on Monday (May 14).

Brigadier-General Cirilito Sobejana, commander of Joint Task Force Sulu, told reporters a Scout Ranger battalion assaulted an Abu Sayyaf lair in Patikul town, in Sulu, at around 6am on Sunday (May 13).

The militants were reported to be holding several hostages in the area, including two policemen abducted on April 29.

The fighting lasted for about an hour, with government troops calling in artillery and air support to flush the rebels out of their camp.

Brig-Gen Sobejana said among those killed were Taha Sawadjaan, a brother of Hatib Sawadjaan, reportedly the Abu Sayyaf's No. 2 man.

Pursuing troops again clashed with fleeing Abu Sayyaf gunmen at around noon, on Monday (May 14).

Brig-Gen Sobejana also reported that three remains, believed to be of militants, were exhumed near the site of Sunday's encounter.

"They look like foreigners. We are still establishing their identities," he said.

The Abu Sayyaf has pledged allegiance to the Islamic State in Iraq and Syria (ISIS). But it is better known for banditry. It has capitalised on decades of instability in the war-torn southern island of Mindanao to generate tens of millions of dollars from piracy and ransom payments.

Since it turned kidnaping into a lucrative trade, the group has beheaded an American, a Malaysian, two Canadians and a German.

A faction led by Isnilon Hapilon took part in the assault on Marawi city in May last year (2017).

Hapilon's fighters, along with those from Marawi's prominent Maute clan and extremists from abroad, stormed and took control of a quarter of Marawi for six months, as they squared off with an entire army division.

Hapilon was killed as the Marawi war drew to a close. But other Abu Sayyaf factions that did not participate in the Marawi siege have remained active in Sulu and in their other stronghold, Jolo province.

rdancel@sph.com.sg