Indonesia's cabinet met to discuss the increasingly fragile ceasefire in Aceh's bloody separatist war, with the armed forces chief suggesting it might decide to scrap the agreement.

"We want to decide on a policy, whether we will continue this peace process or whether we will take another way," General Endriartono Sutarto told reporters before the meeting began. He did not elaborate.

Top security minister Susilo Bambang Yudhoyono was quoted by Monday's Jakarta Post as saying the government has asked for a meeting of the Joint Council – the highest authority supervising the peace pact – to try to salvage the agreement.

Swiss-based mediators the Henry Dunant Centre (HDC) said they had received no request for such a meeting. But HDC spokesman Steve Daly described the peace deal as "very fragile." "My concern is there are people who want to undermine the process," he said.

In the latest violence in the province on Sumatra island, a mob numbering several hundred on Sunday torched an office used by peace monitors.

The HDC said the attack at Langsa in East Aceh, in which no one was hurt, was "clearly organised" – like the March 3 attack on another Joint Security Committee (JSC) office at Takengon in Central Aceh. A human rights group has said an army-backed militia and soldiers were involved in the Takengon attack – an allegation denied by the army.

The HDC said there had also been a number of other threats and acts of intimidation against members of the JSC – which groups representatives from the security forces, the Free Aceh Movement and foreign peace monitors who represent the HDC.

"These are very troubling developments, especially in light of the vast improvements in Aceh's overall safety and security" since the signing of the peace pact on December 9, said a statement late Sunday.

Daly said the Langsa attack was "very much in the mould of Takengon. They came in trucks, came en masse, had a plan ... and even took a lunch break. "As far as Takengon is concerned, there is no police investigation under way, as far as I know." The number of killings has declined dramatically since the agreement, the first to be monitored by foreigners, took effect. But each side in the war, which has claimed an estimated 10,000 lives since 1976, accuses the other of violations.

Jakarta also says the rebels are spreading lies that the peace deal will lead eventually to independence. Daly said each side had reported an equal number of alleged truce violations.

Asked about accusations that the army might have organised the Langsa attack, Sutarto told reporters: "I have not yet heard such reports. But this is just the usual: everything bad is always blamed on us."