Soldiers in the Philippines have clashed with suspected Islamic militants on the southern island of Jolo, according to the military.
Troops have been searching remote islands for suspected militants
Air strikes targeted a base thought to be used by the Abu Sayyaf group. Troops then engaged in heavy fighting with fleeing militants, officials said.
The Philippine authorities have been trying to flush Abu Sayyaf rebels from hideouts in remote island locations.
They are also searching for members of regional terror group Jemaah Islamiah.
A military statement said the assault came after Abu Sayyaf leader Khadafi Janjalani and unidentified Jemaah Islamiah militants were seen in the area.
Major-General Gabriel Habacon of the military's Southern Command said helicopters and gunships were used to drop bombs on the base.
"We've been tracking these terrorists for months," he said. "The time is now. We've located them and we're going to finish them off."
Five hundred soldiers were taking part in the assault, he said. Two had been injured.
Abu Sayyaf is the smallest and most violent militant group in the Philippines. The US has listed it as a terrorist organisation and says it has links to Al-Qaeda.
It is infamous for kidnapping Westerners and Filipinos, beheading victims and receiving large ransom payments. It was blamed for the bombing of a passenger ferry in 2004 which killed more than 100 people.
US-backed military offensives have considerably weakened the group to a few hundred rebels who are mostly on the run, according to the Philippine government.
A number of US troops are based in Jolo, where they are involved in counter-terrorism training.