By OLIVER TEVES, Associated Press Writer Tue Jan 31, 12:17 PM ET

SANTA IGNACIA, Philippines - Philippine troops, backed by rocket-firing helicopters, killed at least 18 communist rebels in a northern farming town Tuesday in their bloodiest clash in months, officials said.

In a separate battle, Philippine marines fought a group of al-Qaida-linked rebels on southern Jolo island Tuesday, killing one Abu Sayyaf militant in a security sweep ahead of joint exercises between U.S. and Philippine troops next month, the military said.

The marines did not suffer any casualties, a military spokesman said. The Abu Sayyaf, which is on a U.S. list of terrorist groups, has been blamed for deadly bombings and kidnappings for ransom in recent years.

In the fighting in the north, four bodies of rebels were brought by helicopter and placed side by side on the ground near a Roman Catholic church, attracting a large crowd of onlookers.

The gunbattle broke out before dawn in a thickly forested mountain area near Santa Ignacia town, about 80 miles north of Manila, when about 25 New People’s Army guerrillas opened fire on approaching army troops, officials said.

Police had received information that the guerrillas planned to attack Santa Ignacia and nearby Mayantok town, and soldiers scaled a mountain area, where the rebels reportedly massed, police Senior Superintendent Nicanor Bartolome said.

Army MG520 helicopters fired rockets on rebel positions, Bartolome said.

Soldiers on the ground killed 18 rebels in the daylong clashes, said military spokesman Lt. Col. Preme Monta. There were no immediate reports of casualties among government troops.

The army has vowed to launch new offensives this year after the guerrillas intensified attacks against military and police targets in recent months. A rebel land mine killed nine army soldiers and wounded 25 in November in central Iloilo province.

The Maoist rebels have been waging a Marxist rebellion since the late 1960s. The military estimates they had more than 8,000 fighters last year, and the rebels claim to have a presence in nearly 70 of the Philippines’ 79 provinces.

The Maoist guerrillas suspended Norwegian-brokered talks with the Philippine government two years ago, mainly to protest Manila’s refusal to ask the United States and the European Union to remove them from terrorist blacklists.

On Jolo, the marines recovered an M-16 rifle from the slain militant following the brief clash in the mountainous coastal town of Patikul, a stronghold of Abu Sayyaf guerrillas, said Col. Domingo Tutaan of the military’s Southern Command.

Government troops have been trying to crush the rebels for years on Jolo, in Sulu province and have stepped up security patrols before at least 250 American soldiers arrive for annual joint military exercises called "Balikatan," officials said.

The military exercises on Jolo will focus on humanitarian missions, including dental treatments and building classrooms. Joint maneuvers will be held simultaneously in the northern and central Philippines, officials said.

"The Balikatan in Sulu is part of our efforts to curb terrorism and to improve the security there," Tutaan said. "The idea is to build a community that is unfriendly to terrorists."

U.S.-backed military offensives have reduced Abu Sayyaf to a few hundred rebels who are mostly on the run, the military says.