MANILA, May 13 (Xinhua) -- Four people were injured in a grenade explosion after they cast their votes at a school in Marawi City, capital city of Lanao province in southern Philippines Monday afternoon, the military said.
The injured included a son of the Marawi city mayor, said Danielo Lucero, commander of the Army's 1st Infantry Division.
The grenade was hurled by an unidentified suspect at the rooftop of the school at around 3 p.m. The grenade rolled down and then exploded, Lucero's spokesman, Jeffer Somera said.
Lucero said troops from the Army's 15th Infantry Battalion promptly responded to the scene to secure Precinct Count Optical Scan (PCOS) machines and the election inspectors inside.
The four victims had just finished casting their votes when the explosion occurred. They were taken to a nearby hospital for treatment, Lucero said.
The Philippine midterm elections commenced across the country on Monday. More than 52,000 Filipinos trooped to their election precincts Monday to cast their votes for both local and national positions.
Elections in the Philippines have long been marked with violence. Killings due to intense political rivalries, particularly in the provinces, usually occur during elections in the Philippines, with more than 50 deaths in 60 cases before this year's election.