The man – identified as Jafar Gamo Sultan – was detained during a hunt for four suspects believed to be behind the attack on worshippers in Marawi, the country’s largest Muslim city, which was besieged by militants in 2017.
Four people were killed and 50 wounded in the bombing last Sunday that was later claimed by the Islamic State group.
Brigadier-General Yegor Rey Barroquillo said surveillance footage appeared to show Sultan carrying the explosive device hidden in a bag into the Mindanao State University gymnasium, where worshippers had gathered for the service.
Will Philippine peace talks end rebel conflict for good or ‘aid the enemy’?
Will Philippine peace talks end rebel conflict for good or ‘aid the enemy’?
Barroquillo, who commands the 103rd Brigade of the Philippine Army, which is involved in the search for the assailants, said one of Sultan’s relatives, a man called “Omar”, was also wanted over the attack.
All four men belonged to the Dawlah Islamiyah-Maute group and were suspected of being “part of a cell” that carried out the attack, Barroquillo said.
The military has described the bombing as a possible revenge attack for their deadly operations against militant groups in the region.
Philippines stands out in Asean over embrace of US’ Indo-Pacific strategy
Philippines stands out in Asean over embrace of US’ Indo-Pacific strategy
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.