At least 15 people have been killed in a double bomb attack in the southern Philippines.

Devices exploded near a government office and a Roman Catholic church in Isabela on Basilan island, south of Mindanao. Police say five people who were involved in the bombings are among the dead. The other victims were soldiers, police officers and civilians.

The Philippine authorities say the bombers wore police uniforms. The attacks are being blamed on an extremist Muslim group along the lines of Abu Sayyaf, which has links with al-Qaeda.

The Philippine army estimates about 400 rebels are operating on Basilan and other islands in the southern Philippines, an area with a reputation for being a stronghold of Islamic extremists.