MANILA, Philippines (AP) — Suspected Islamic militants set off powerful bombs in a southern Philippine town Monday, killing at least 10 soldiers and civilians despite extra tight security because of threats of attacks by the Islamic State group-aligned militants, military officials said.

Regional military commander Lt. Gen. Corleto Vinluan said at least five soldiers and four civilians were killed in the first attack when a bomb attached to a motorcycle exploded at noon near two parked army trucks in front of a grocery and a computer shop in Jolo town in Sulu province.

“It was a vehicle-borne improvised explosive device which exploded while our soldiers were on a marketing run,” Vinluan told reporters.

A second blast nearby, apparently from a female suicide attacker, occurred about an hour later and killed the bomber and a soldier, Vinluan and other officials said. “A soldier was checking on somebody then there was another explosion,” Vinluan said.

A third unexploded bomb was reportedly found in a public market. Jolo was immediately placed in a security lockdown by troops and police.

Nearly 40 soldiers, police and civilians were wounded in the bomb attacks, military and police officials said.

Pictures seen by The Associated Press showed soldiers carrying a man from the scene of the explosion near an army truck while another blast victim lay on the road. The wreckage of a motorcycle and partial remains were seen on the road.

The first bombing was carried out near a town plaza and a Roman Catholic cathedral in the predominantly Muslim province. The country’s southern region is home to minority Muslims in the largely Roman Catholic nation and has been the scene of decades of Muslim separatist unrest, particularly in far-flung island provinces like Jolo.

There was no immediate claim of responsibility for the attack, but the military blamed an Abu Sayyaf militant commander, Mundi Sawadjaan, for the bombings.

Military officials said last week that Sawadjaan plans to launch bombings in Sulu using two female suicide attackers. Army troops were carrying out a covert operation to locate and capture Sawadjaan and the suicide bombers in June when four army personnel were stopped at a Jolo police checkpoint and later shot to death by police personnel.

The army angrily described the killings as a rubout and demanded murder charges to be filed against nine policemen. Police officials, however, say it may have been a mistaken encounter between the army and police forces.

The military has been waging a months-long offensive against the Abu Sayyaf, a small but violent group aligned with the Islamic State group and blacklisted by the United States and the Philippines as a terrorist group for past bombings, ransom kidnappings and beheadings.

The number of its armed fighters have dwindled to a few hundreds in recent years due to battle setbacks and surrenders, including a key commander, Abduljihad Susukan, who gave up to authorities two weeks ago after being wounded in battle.

Susukan has been blamed for kidnappings and beheadings of hostages, including foreign tourists, and surrenders through a Muslim rebel chief, who has signed a peace deal and was cooperating with the government. He is now in police custody and faces multiple murder charges.

Military officials said they were not discounting the possibility that Monday’s bombings may have been staged partly as a retaliation for the detention of Susukan, who is now in police custody and faces multiple murder and kidnapping charges.