A soldier lays on a stretcher and is carried by his comrades inside the Camp Bautista hospital after sustaining wounds in a gunfight with Islamic State-linked Abu Sayyaf militants in Talipao town, Sulu province, Philippines. REUTERS/Nickee Butlangan

MANILA (Reuters) - Philippine soldiers killed “more than 10” Islamic State-linked Abu Sayyaf militants in an attempt to free Vietnamese captives held on a remote southern island as troops fired howitzer shells on rebel positions, an army general said on Monday.

The small but violent militant group, known for extortion, beheading and kidnap-for-ransom activities, is holding more than two dozen captives on Jolo island. It beheaded a German captive two months ago when no ransom was paid for his release.

Major-General Carlito Galvez, military commander of western Mindanao, said 32 soldiers were also wounded in Sunday’s assault on an Abu Sayyaf hideout in Talipao town, where the militants were believed to be holding six Vietnamese captives.

“The 105mm howitzer directly hit enemy positions,” Galvez told reporters, saying four rounds were fired when advancing troops were pinned down.

“More than 10 were killed. Our troops had discovered mangled bodies in the area, but we continue to pursue them.”

There was no word on the fate of the captives. Four of the wounded soldiers were airlifted to a hospital while 28, among them a battalion commander, had minor shrapnel wounds from grenade blasts.

Galvez said troops had clashed for more than an hour with about 100 Abu Sayyaf rebels led by Radullan Sahiron, a one-armed militant leader who figures on the U.S. State Department’s wanted list, with a $1-million bounty.

Last month, five Malaysians were freed on Jolo and two Filipino sailors were rescued on nearby Basilan island by soldiers chasing the Abu Sayyaf militant group.