MANILA (BLOOMBERG) - The Philippine military launched an airstrike against a local terrorist group suspected to be behind a deadly attack on a Catholic church on the southern island of Mindanao on Sunday (Jan 27).

The authorities have intensified operations against a splinter group from the Abu Sayyaf in the southern province of Sulu, Philippine Defence Secretary Delfin Lorenzana said on Wednesday, including an airstrike in parts of Jolo town on Tuesday.

At least 21 people were killed and more than a hundred injured in two explosions at the Catholic church in Sulu.

President Rodrigo Duterte's directive is to "crush the Abu Sayyaf", Mr Lorenzana said. The military has been receiving reports of a possible terrorist attack in the province as early as August last year, he said.

Investigators are still looking at other suspects in the attack, including a Yemeni couple who may have carried out suicide bombings at the church, according to the defence chief.

On Wednesday, two people died and four others were injured when a grenade exploded in a mosque in Zamboanga City, the second explosion in Mindanao in four days.