The attack happened during a mass at the sports hall of Mindanao State University in Marawi. That city is the most important Muslim city in the archipelago, which is predominantly Christian. In 2017, the city was under siege by Islamic militants for five months.
The attack comes three days after a Philippine Air Force attack in Mindanao killed three Islamic militants from the Dawlah Islamiya-Philippine organization. Police Commissioner Allan Nobleza says the investigation to determine whether this attack is linked to the military operation is ongoing. An act of revenge by IS supporters is certainly one of the options.
The university posted a statement condemning the act of violence. Classes are suspended and more security personnel are deployed on campus.