The blast happened Sunday at Mindanao State University's gymnasium in Marawi (File)
A Philippine military commander said Monday that a "massive" manhunt was underway for the assailants who bombed a Catholic mass in the country's restive south, killing four worshippers and wounding dozens.
The blast, claimed by the Islamic State group, happened Sunday at Mindanao State University's gymnasium in Marawi, the country's largest Muslim city, which was besieged by Islamist militant groups in 2017.
Security officials have said the bombing, which wounded around 50 people, may have been a retaliatory attack for a series of military operations against Islamist militant groups in recent days that killed multiple fighters.
"There's an ongoing massive operation to hunt the terrorist groups or the suspected perpetrators of the bombing," Western Mindanao Command chief Lieutenant General William Gonzales told a press conference.
"Rest assured the military here will go after the perpetrators. We will see to it that the people here will be secured and safe, that will be our commitment."
On Sunday, President Ferdinand Marcos blamed "foreign terrorists" for the attack and his defence chief Gilbert Teodoro said there were "strong indications of a foreign element".
Before Islamic State claimed responsibility, military chief General Romeo Brawner had said the bombing may have been a revenge attack for government operations against three Islamist militant groups -- Dawlah Islamiyah-Philippines, Abu Sayyaf and Maute -- in western Mindanao in recent days.
Pro-Islamic State Maute and Abu Sayyaf militants -- including foreign and local fighters -- held Marawi under siege in 2017.
The Philippine military wrested back the ruined city after a five-month battle that claimed more than 1,000 lives.
Militant attacks on buses, Catholic churches and public markets have been a feature of decades-long unrest in the region.
Manila signed a peace pact with the nation's largest rebel group, the Moro Islamic Liberation Front, in 2014, ending their deadly armed rebellion.
But smaller bands of Muslim fighters opposed to the peace deal remain, including militants professing allegiance to the Islamic State group. Communist rebels also operate in the region.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)