The first blast killed two civilians and wounded 20 other churchgoers inside the Jolo Cathedral in Sulu province, while a second blast killed five soldiers in the parking lot of the church, said Colonel Gerry Besana, spokesman of the military's Western Mindanao Command.
The second explosive device was detonated as the soldiers responded to the initial attack inside the church, and 15 other members of the security forces were wounded, Besana said.
The government's plan to create a self-administered area for the Muslim-dominated parts of Mindanao was backed by 85 percent of voters in a referendum last Monday, paving the way for a three-year transition towards elections for a legislature that will choose an executive.