The victims were in a van in Datu Saudi Ampatuan town in Maguindanao province Tuesday night when the improvised bomb went off. Norodin Macabangen, a municipal treasurer of a nearby town, died in hospital. His six-year-old daughter, a brother and another man died instantly while his wife and 9-year-old son were injured.
A police report said there had been a firefight between soldiers and Bangsamoro Islamic Freedom Fighters in the area, and that the explosives were believed intended for reinforcement troops.
The hard-line rebels broke off several years ago from the larger Moro Islamic Liberation Front when the latter pursued peace talks with the government, opting to continue to fight for a separate homeland in the south for minority Muslims in the predominantly Catholic Philippines.