The Philippine military says Muslim militants have ambushed security guards and labourers from a rubber plantation on a volatile southern island, killing three men and wounding six others.

The attack Thursday on Basilan Island, the stronghold of al-Qaeda-linked Abu Sayyaf militants, is the latest in weeklong assaults against the 1,200-hectare plantation despite the military’s efforts to protect workers.

The government blames the Abu Sayyaf, which is notorious for ransom kidnappings and terrorist attacks over the last two decades. The violence is reportedly rooted in a labour dispute involving the cooperative and dismissed members who are relatives of some of the militant commanders.