At least 20 Philippine soldiers have been killed by suspected Islamic rebels on the southern island of Jolo.
Ten of the victims died when gunmen ambushed a military convoy near the town of Maimbung.
Troops were sent to engage the rebels, and during the battle which followed, 10 more soldiers died.
Military spokesmen have blamed the Moro National Liberation Front (MNLF) and Abu Sayyaf - an Islamic militant group with alleged ties to al-Qaeda.
Abu Sayyaf has been blamed for various kidnappings and bombings, including an attack on a ferry in 2004 that killed more than 100 people.
The MNLF signed a peace treaty with Manila in 1996, but some of its members have refused to disarm.
Thousands of Philippine troops are based in Jolo, some 950km (600 miles) south of the Philippine capital, Manila.
They have been fighting Islamic militants holed up in the island's mountainous terrain for several months.
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