The Philippine army has clashed with hundreds of separatist Muslim rebels in a second day of violence on the southern island of Jolo.
Extra troops are being sent to Jolo to help quell the unrest
At least 14 soldiers have been killed and 16 injured in a series of attacks, according to army sources.
The number of dead and wounded rebels is unknown.
The clashes began on Monday, when more than 500 rebels loyal to separatist leader Nur Misuari attacked troops in retaliation for a recent army assault.
A huge military operation was launched last week, to target the armed Muslim group Abu Sayyaf - an al-Qaeda linked organisation which is also alleged to have ties with the Misuari faction.
General Alberto Braganza, military chief in the southern Philippines, said Misuari's supporters were using the attack on Abu Sayyaf as a pretext to pressurize the authorities to have Misuari transferred from a prison near Manila to one in Jolo.
Misuari used to be the head of the separatist Moro National Liberation Front (MNLF), which signed a peace treaty with Manila in 1996.
But the violence continued and Misuari was jailed on charges of rebellion in 2001.
The latest skirmishes have been concentrated in several towns around Jolo, a known stronghold for Islamic militants.
Thirteen soldiers were killed in the town of Patikul on Monday, according to police sources.
About 300 rebel gunmen are also said to have occupied an army compound in Panamao.
In the nearby town of Parang, another 80 suspected rebels attacked a group of soldiers, killing one and wounding several others.
Brigadier General Agustin Demaala said he was urging the rebels to stop their attacks, stressing that Abu Sayyaf - not followers of Nur Misuari - were the target of the recent government offensive.