The group of countries in southeast Asia known as ASEAN has strongly condemned the bombing of a church service in the southern Philippines, which it called a "heinous terrorist attack".  Four people were killed in the explosion at a Catholic Mass last weekend.

"We extend our deepest condolences to the bereaved families," the Association of Southeast Asian Nations said in a statement.

The bomb went off on Sunday during a service at a university gymnasium in Marawi, leaving the local Christian community in total shock.  Their city was left in ruins five years ago, after a five-month military campaign to end an occupation by Islamic State loyalists that triggered alarm in Asia about the group's influence.

The majority of the Philippines identifies as Catholic, but the country's second largest island of Mindanao in the south is home to a significant Muslim population.  The region has been subject to kidnappings, terror activity and clashes between the military and insurgent groups.  Both the UK Foreign Office, and US State department advise against travel to the area. 

Islamic State militants have claimed responsibility for last Sunday's attack.  President Ferdinand Marcos Jr said "foreign terrorists" were behind it and police said they were investigating the incident, and working to validate the claim by the Islamic State group. 

Philippine police say they have identified two suspects from Daulah-Islamiyah Maute, a local group involved in the 2017 seizure of Marawi alongside fighters from Indonesia, Malaysia and beyond. 

On Friday the Philippine military announced the arrest of a man in Marawi who is suspected of placing the bomb in the gymnasium, having been being identified by witnesses.