Nine people were wounded when five grenades exploded outside a polling station in a restive region of the southern Philippines hours before voting began in national elections, police said Monday.
Elections are a traditionally volatile time in a country with lax gun laws and a violent political culture, but police said this season has been comparatively peaceful.
The attack happened late Sunday in Datu Unsay municipality on Mindanao island, a haven for multiple armed groups ranging from communist insurgents to Islamist militants.
Minutes later, a grenade exploded in the neighbouring municipality of Shariff Aguak, but there were no casualties. Both towns are located in Maguindanao province.
Police said the victims had walked from their remote mountain villages to cast their votes at the municipal hall when polling stations opened at 6:00 am (2200 GMT Sunday) on Monday across the archipelago.
"It is their custom to come down early from their villages, which are located eight to 12 hours away on foot," said provincial police spokesman Major Roldan Kuntong.
In 2009, Maguindanao was the scene of the country's deadliest single incident of political violence on record.
Fifty-eight people were massacred as gunmen allegedly working for a local warlord attacked a group of people to stop a rival from filing his election candidacy.
Dozens of the victims were journalists covering the contest.
A spokesman for the Commission on Elections said they were trying to verify if Sunday night's grenade explosions were election-related.
Vice presidential frontrunner Sara Duterte, who is the former mayor of Mindanao's Davao City told reporters she hoped voters would not end up "disenfranchised" as a result of the violence.
More than 18,000 posts, from president to town councillor, are up for grabs in the elections.
The son of former dictator Ferdinand Marcos is the favourite to win the presidential vote, which would return the clan to the pinnacle of political power.
Rights groups, Catholic church leaders and opponents see the elections as a make-or-break moment for the country's democracy, amid fears Marcos Junior could rule with a heavy fist.
Thousands of personnel from the police, armed forces and coast guard have fanned out across the archipelago to help secure polling stations and ballots, escort election officials and guard checkpoints.
As of Sunday, there had been 16 "validated election-related incidents" since January 9, including four shootings and a "slight illegal detention", said national police spokesman Brigadier-General Roderick Alba.
That compares with 133 incidents during the 2016 presidential elections and 60 in the 2019 mid-term polls.