By Hader Glang

ZAMBOANGA CITY, Philippines

A bomb explosion rocked the majority Muslim province of Sulu on Saturday night, leaving four people dead and over a dozen injured, the military said.

Army Colonel Cirilito Sobejana, commander of the Joint Task Force Sulu, said the bomb went off along the road of sitio Lambayon in Busbos, an adjacent town of the capital of Jolo, at around 7p.m. (1100 GMT).

Citing an initial police investigation, Sobejana said one of the four fatalities was minor and the 18 blast victims were rushed to a nearby hospital for shrapnel wounds.

Sobejana said responding security forces held one person, who might have planted an improvised explosive, now under police custody and the incident was currently being investigated.

No one claimed responsibility for the attack. But the military blamed the Abu Sayyaf for recent bombings in Sulu, a known stronghold of the Daesh-linked terror group which has beheaded foreign hostages including a Malaysian, two Canadians, and a German after ransom failed to be given to the group.

On Thursday, two of the five Malaysian sailors being held hostage since last year had been rescued by government troops in Sulu.

Also on Saturday, a Filipino tugboat skipper was rescued by government troops, two days after he was abducted with another crewman in the waters off Sibago Island in Basilan.

The military said Captain Aurelio Agac-ac of Panamanian-flagged MV Super Shuttle Roro 9 and his chief engineer Laurencio Tiro were seized by the Abu Sayyaf group Thursday afternoon.

Meanwhile, Western Mindanao Command chief Maj. Gen. Carlito Galvez confirmed that the Abu Sayyaf group suffered two casualties and two were captured during the rescue operations.

He said the tracking operations of scout rangers and special forces are ongoing. "And hopefully in due time we will rescue the remaining hostage."

According to Galvez, the rescue of Aurelio Agac-ac is a result of a combined effort of the troops, the Philippine National Police, Civilian Volunteer Organizations, local government and the community.

"Again, Western Mindanao Command will exhaust all means to track these kidnappers and rescue the other victims. This time, the effort will be stronger as it is backed by the peace-loving people of Western Mindanao."

Since 1991, the group -- armed with mostly improvised explosive devices, mortars and automatic rifles -- has carried out bombings, kidnappings, assassinations and extortion.