Chief Inspector Dario Caladrana, police chief of Tantangan, South Cotabato, said the blast occurred at 6:16 p.m. at the town’s public market.
He identified the victims as Rogelio Olarte, 59, Almeda Pabistan, 31, and three teenagers aged 12 and 15, all residents of Poblacion Tantangan, about two hour driver from here.
Caladrana said police were still investigating the motive for the explosion which occurred at the busy public market cum terminal for tricycles and jeepneys.
No one has claimed responsibility.
Police said the IED fashioned from 60-millimeter mortar with mobile phone as trigger mechanism could have been intended to other areas but left at the market due to the presence of policemen.