MANILA, December 16, 2010 (AFP) – Philippine security forces and communist rebels began a Christmas ceasefire on Thursday in the shadow of the guerrillas’ deadliest attack in a year and marred within hours by a fresh skirmish.

Both the government and the rebels declared 18-day ceasefires from midnight (1600 GMT) Wednesday ahead of the first formal peace talks in six years seeking to end the decades-old Maoist rebellion that has claimed thousands of lives.

The military will observe an 18-day ceasefire but remains on guard, after the New People’s Army (NPA) killed 10 soldiers two days ago in an attack that also left a boy dead, military spokesman Brigadier-General Jose Mabanta said.

“You can see the treachery involved. It is far from being an act of good faith,” said Mabanta, referring to the ambush in the central island of Samar on Tuesday.

The government peace negotiating panel expressed concern over the deadly ambush but also stressed that the peace process should continue.

“Despite this treacherous attack in the eve of the observance of the ceasefires declared by both sides, we believe that the course to genuine peace is the appropriate answer to the current conflict,” the panel said in a statement.

NPA guerrillas killed 10 soldiers as they were returning to their camp to observe the ceasefire on Tuesday. A nine-year-old boy was killed in the crossfire, the military said.

Although the ambush took place before the start of the ceasefire, Mabanta said the incident cast doubt on the insurgents’ sincerity.

“We have done our part. It is up to them on their part to show some act of sincerity,” he told AFP.

Defence Secretary Voltaire Gazmin said the government would file a protest but stressed that the military would respect the ceasefire and would not retaliate.

Just four hours after the truce took effect, soldiers and NPA guerrillas clashed in the southern island of Mindanao although there were no casualties on either sides, said local military spokesman Major Eugenio Julio Osias.

The peace panel declined to comment on this incident until it received further details.

An NPA statement issued in Manila said the group was respecting the ceasefire but accused the military of violating it by sending troops to a rebel-influenced area north of Manila.

“We are prepared to give battle if military and police troops intrude in any NPA positions,” the statement said.

The Christmas ceasefire is intended to pave the way for the resumption of peace talks between the government and the 5,000-strong communist rebel movement.

Chief government negotiator Alexander Padilla earlier said talks would begin in Norway in February next year, aimed at ending the insurgency in three years.

The NPA launched its uprising in 1969, and thousands of people have been killed during what has become one of Asia’s longest-running insurgencies.