Clashes between the Filipino army and Islamist militants with links to the Islamic State (Isis) and al-Qaida left at least 14 dead in the restive south of the country, military officials said.
Five soldiers and nine gunmen with the Abu Sayyaf extremist group were killed in the gun battle that broke out in Sulu province's mountainous Talipao town, army Col. Allan Arrojado said.
A further 26 soldiers and 30 militants were wounded.
After a five hour gun battle, government forces were in hot pursuit with 300 extremists who split into smaller groups and pulled back, Arrojado said.
"We are tracking their whereabouts," he said.
Founded in the early 1990s, Abu Sayyaf has developed a fearsome reputation for its use of bomb attacks, abductions and extortion.
The group has also kidnapped several foreigners, including a Dutch and a Swiss birdwatchers, holding them hostage in Sulu's dense jungles.
In October, two German tourists were released after weeks in captivity amid claims that a 250 million peso (£3.5m) ransom was paid.
Abu Sayyaf, a loose group numbering several hundred fighters, uses ransom money to fund its Islamic separatism campaign in southern Philippines.
One of its leaders, Isnilon Hapilon, who has a $5m bounty on his head, recently pledged allegiance to the Islamic State group operating in Syria and Iraq.