Manila, Dec 3 , An explosion occurred inside a gym of Mindanao State University in Marawi City, Lanao del Sur province, in the southern Philippines, killing at least three and injuring seven, local media reported on Sunday.
The blast occurred past 7 a.m. local time when students and teachers gathered for a Catholic mass inside the gym, according to local police, Xinhua news agency reported.
Police were investigating the type of explosive device used in the blast.
Marawi City is the capital and the largest city of Lanao del Sur on Mindanao island.
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