Cotabato City, Philippines - One soldier was killed in a clash with Muslim separatist rebels in the southern Philippines, where the guerrillas are reportedly gathering following a setback in peace talks with the government, officials said Tuesday.

The firefight erupted Tuesday when about 50 Moro Islamic Liberation Front (MILF) rebels stormed a sugarcane plantation in Aleosan town, North Cotabato province, 930 kilometres south of Manila, said army Major Randolph Cabangbang, a regional military spokesman.

Cabangbang said government troops responded to the attack, triggering a firefight that killed one soldier.

He said the rebels raided and burned the 10-hectare plantation.

"This is part of the rebels' build-up in the province," he said.

North Cotabato Governor Jesus Sacdalan said MILF rebels have been massing up in the province since the Philippine Supreme Court on Monday stopped the signing of a controversial land deal between the guerrilla group and the government.

"The villagers are alarmed," he said. "The move is prohibited as massing up of troops is a violating of the existing ceasefire agreement between the MILF and the government."

Sacdalan said the MILF forces in the province were reportedly led by Ustadz Amerial Umbra Kato, a rebel commander trained in Afghanistan.

"Majority of the rebels are coming from other areas, such as Camp Darapanan, the MILF's main lair in nearby Sultan Kudarat province," he said.

The Philippine government and the MILF were supposed to sign on Tuesday an agreement on ancestral domain that would have provided for the holding of a plebiscite to expand an existing autonomous Muslim region in the southern region of Mindanao.

But Catholic politicians in Mindanao asked the Supreme Court to stop the signing and to nullify the agreement, which they alleged violated the constitution.

General Alexander Yano, armed forces chief of staff, assured residents in North Cotabato that the military was closely monitoring the situation in the province and the southern region of Mindanao following the setback in the peace talks.

"We have clear instructions from President Gloria Macapagal Arroyo to be vigilant amid the recent developments," Yano said. "We are likewise directed to take appropriate actions, while upholding the primacy of the peace process, to protect the citizens from harm."

The signing of the ancestral domain deal is a key step in resuming formal peace talks between the government and the MILF, which have been stalled since December 2007.

Aside from expanding the existing six-province Autonomous Region in Muslim Mindanao by holding a plebiscite in more than 700 village in 2009, the agreement also provides for the set-up of a new form of government for Muslims after a final peace deal is reached.

The 11,000-strong MILF has been fighting for the establishment of an independent Islamic state in Mindanao since 1978. It agreed to hold peace talks with the government in 1997 in hopes of ending the violent separatist struggle. (dpa)