Monitoring aftermath of bombing attack on a university gymnasium in the southern Philippines Sunday.

The ISIL group has claimed responsibility.

A military official said Monday that a “massive” manhunt is under way for the attackers.

An explosion ripped through a gymnasium at Mindanao State University in Marawi City during a Catholic mass service on Sun morning killing four people and leaving several others injured.

Defence Secretary Gilberto Teodoro told a press conference there were “strong indications of a foreign element”.

Although relatively peaceful in recent months, Mindanao has for decades been racked by violence amid a rebellion by religious armed groups.

On Saturday, the Philippine military had announced that it had killed 11 armed fighters in an operation about 200km from Marawi.

Philippine security officials had suggested on Sunday the attack may have been retaliation for this military operation.

In 2017, Marawi was the site of a bloody urban battle between ISIL fighters and government forces. Armed fighters had laid siege to the city in 2017, prompting months of heavy combat that prompted hundreds of thousands to flee and left more than 1000 dead.

Aljazeera.