Philippine military officials say 16 troops and about 30 Muslim extremists have been killed in clashes in the southern Philippines.

Officials say fighting erupted after government forces launched an attack on an Abu Sayyaf rebel camp outside the town of Ungkaya Pukan on Basilan island.

Fifteen soldiers were killed in the fighting. A helicopter pilot was also killed after his gunship was shot down while it was supporting troops on the ground.

The fighting was one of the bloodiest clashes on Basilan since 14 marines were killed in an ambush last month.

The United States considers Abu Sayyaf a terrorist group with ties to the radical Jemaah Islamiyah organization. Philippine forces have been on the offensive against Abu Sayyaf since 2005, fighting primarily on Jolo.

The al-Qaida-linked group is blamed for several deadly attacks in the Philippines, including a 2004 bombing that gutted a ferry and killed 116 people.

Some information for this report was provided by AFP, AP and Reuters.