The bomb went off on Sunday during a service at a university gymnasium in Marawi, a city left in ruins in 2017 by a five-month military campaign to end an occupation by Islamic State loyalists that triggered alarm in Asia about the group’s influence.

“We extend our deepest condolences to the bereaved families,” Asean said in a statement.

Islamic State militants claimed responsibility for Sunday’s attack. President Ferdinand Marcos Jr said “foreign terrorists” were behind it and police said they were investigating the incident and validating the claim by the Islamic State group.

Police had identified as suspects two members of Daulah-Islamiyah Maute, a local group involved in the 2017 seizure of Marawi alongside fighters from Indonesia, Malaysia and beyond.

The Philippine military on Friday announced the Dec 6 arrest in Marawi of a man suspected of placing the bomb in the gymnasium having been being identified by witnesses.