At least three people were killed and seven others injured in a bomb attack on Sunday, December 3, during a Catholic mass in the southern Philippines.

The explosion occurred during a mass in the gymnasium of Mindanao State University in Marawi, the country’s largest Muslim city, regional police chief Allan Nobleza said. “We are investigating to determine whether it is an improvised explosive device or a grenade,” Nobleza said.

Mindanao State University issued a statement condemning the “act of violence,” while suspending classes and deploying more security personnel to campus. “We stand in solidarity with our Christian community and all those affected by this tragedy,” the university said in a statement.

Marawi City Mayor Majul Gandamra urged members of the Muslim and Christian communities to remain united. “Our city has long been a symbol of peaceful coexistence and harmony, and we will not allow such acts of violence to overshadow our collective commitment to peace and unity,” Gandamra said.

Military operation

Photos posted on the Lanao del Sur provincial government’s Facebook page show the governor, Mamintal Adiong, visiting “victims injured in the bomb attack” at a medical facility.

The attack came after an airstrike by the Philippine army on Friday killed eleven Islamist militants from the Dawlah Islamiya-Philippine organization in Mindanao. Nobleza said police were investigating whether Sunday’s attack was linked to the military operation.

The army said on Saturday that the Islamist organization had planned to stage attacks in the province of Maguindanao del Sur. Lanao del Sur and Maguindanao del Sur are part of the Bangsamoro Autonomous Region in Muslim Mindanao.

Insurgent bands

Militant attacks on buses, Catholic churches and public markets are a feature of the unrest that has rocked the region for decades. In 2014, Manila signed a peace pact with the country’s largest rebel group, the Moro National Liberation Front, ending their bloody armed insurgency.

But there remain small bands of Muslim insurgents opposed to the peace deal, including militants who have pledged allegiance to the Islamic State (IS) organization. Communist rebels also operate in the region.

In May 2017, hundreds of foreign and local pro-IS gunmen seized Marawi. The Philippine army had retaken the ruined city after a five-month battle that cost more than a thousand lives.

Another line of investigation is whether remnants of Maute and Abu Sayyaf Islamist groups, which participated in the siege of Marawi, are involved, Mr. Nobleza said.