At least 15 fishermen were killed and three others wounded in the southern Philippines when gunmen opened fire on three boats, military officials have announced.
The incident happened on Monday in Basilan province, a stronghold of Muslim rebels.
A military spokesman said it was likely caused by rivalry over fishing turf.
Police have identified several suspects involved.
"They (the victims) were fishing on another group's turf," regional military spokesman Lt Col Randolph Cabangbang told the Agence France Presse news agency.
He added that the possibility of Islamist militants or Muslim guerrillas being involved in the incident had so far been ruled out.
The shooting was discovered by other fishermen in the area. The victims were residents of Pagadian city, 160km north-east of Basilan.