Philippine communist guerrillas killed 11 soldiers and a civilian on Wednesday in one of their most audacious attacks in recent years, the military said.
A three-vehicle Philippine army convoy was ambushed by New People's Army (NPA) rebels near the mountain town of Tinoc on the main island of Luzon, said Major-General Rommel Gomez, army commander of the northern Philippines.
"These people are terrorists," Gomez said of the attackers. "We are still on pursuit operations."
An army captain was among 11 soldiers killed in the early morning attack, army spokesman Colonel Loreto Maguddayao told AFP, and a civilian who played in a military brass band also died.
Two other soldiers and another civilian were wounded.
"This is considered one of the most daring attacks by the NPA in this area in recent years," Maguddayao said.
The apparent target was the local battalion commander, Lieutenant-Colonel Eugenio Batara, who was also in the convoy as it drove back to camp after visiting a remote mountain outpost but escaped unhurt, Maguddayao added.
About 100 soldiers, policemen and police aides were killed in NPA attacks across the country last year, down from 184 in the previous year, the military has said.
The NPA is the armed unit of the Communist Party of the Philippines, and has been waging one of Asia's longest running communist insurgencies since 1969.
The government last year boasted it had decimated the NPA ranks in the northern mountain regions due to successes on the battlefield and effective community work that turned villagers against the rebels.
Across the Philippines, the military said the NPA's strength had fallen to a around 4,000 fighters as of 2011, from more than 26,000 at its peak in the 1980s.
The government re-opened peace talks with the communists in February last year, with both sides agreeing to work towards a June 2012 deadline to sign a peace deal.
But the negotiations hit an impasse in November when Manila rejected rebel demands to free 18 jailed guerrillas the NPA said were consultants to its talks team.
The rebels have since vowed to step up attacks against the military and vital government installations.
The impasse also came a month after a major rebel action involving about 200 guerrillas attacked three mining sites in the mineral-rich but poverty-stricken southern island of Mindanao.
The NPA claimed the attacks were payback for years of alleged environmental damage and abuse by the miners, but the military said they were carried out to force companies to pay illegal "revolutionary taxes".
