No group has claimed responsibility for the blast yet and it was not yet clear if terrorist groups were involved, police said.
The two men reportedly have lived on the restive southern island of Mindanao since they were separated from their\ndivision, staying on for fear they would face court-martial if they returned to Japan.
Manny Pacquiao's loss to undefeated American Floyd Mayweather Jr in their welterweight showdown in Las Vegas was met with tears, anger and accusations of foul play in his homeland of the Philippines on Sunday.