COTABATO - A bomb ripped through an internet cafe in the southern Philippines on Sunday, killing one person and wounding 15 in the second deadly blast to strike the same city in days, authorities said.

The explosion in Isulan was a short distance from where an improvised bomb under a motorcycle blew up on August 28, killing three and wounding dozens. These attacks are the latest violence in the south of the majority Catholic archipelago, where Islamist militants have been fighting a decades-long insurgency.

There was no immediate claim of responsibility for Sunday's bombing, but authorities' suspicion immediately fell on the Islamic State-linked Bangsamoro Islamic Freedom Fighters (BIFF). "It is the BIFF who is responsible," Army General Cirilito Sobejana told AFP. "This group is out to sow chaos."

The mayor's office of Isulan and the military said one person was killed in the bombing and 15 were wounded, four of whom were in critical condition. The recent blasts follow President Rodrigo Duterte's government enacting a law to create greater autonomy for the Muslim minority in the south which is hoped to help end the conflict.

Authorities have expressed worry the law could encourage some militant factions to attack in an effort to derail the peace efforts. Several armed groups are active against government forces in the south of the Southeast Asian country, where a decades-long rebellion has claimed more than 100,000 lives according to a government count.

Duterte put the southern Philippines under martial rule until the end of this year after pro-IS militants seized the southern city of Marawi last year.