A female activist faces 20 years in jail if found guilty in a treason trial which began in Indonesia's Aceh province, where troops are battling separatist rebels.

Prosecutors charged Cut Nur Asyikin, 48, with treason and "sinister conspiracy" by joining rallies in the provincial capital Banda Aceh in November 1999 and 2000 which called for a referendum on independence from Indonesia.

Chief prosecutor Muhi Buddin said Asyikin, who heads the Srikandi non-government organisation for empowerment of women, had in a November 1999 rally spoken about how Acehnese "must continue fighting by way of referendum." "In her speech, the defendant showed her rejection of the government's effort to solve the conflict peacefully through the special autonomy status," Buddin told the district court.

Buddin, quoting what he said was Asyikin's speech, said the defendant had told Acehnese that they "should fight by way of war" if they cannot hold a referendum.

The military on May 19 this year launched a huge operation to crush guerrillas of the Free Aceh Movement (GAM), who have been fighting for independence since 1976 and who reject Jakarta's granting of special autonomy. Authorities have also announced plans to prosecute numerous civilian activists seen as sympathetic to the rebels' cause. The head of the Aceh Referendum Information Centre, Muhammad Nazar, was jailed for five years in July for sedition.

Asyikin, who owns the Rajawali hotel in Banda Aceh, was arrested there by police on May 20 and has been detained since.

Also on trial are five former GAM peace negotiators, who were arrested shortly after last-ditch peace talks with the Indonesian government broke down in Tokyo. The five had been due to join GAM's team in Tokyo in May but were arrested on their way to the airport. Aceh police freed them as the Tokyo talks began but rearrested them when negotiations broke down and the military offensive was launched.

Judges in the trial of Sofyan Ibrahim Tiba, one of the five, ruled Tuesday that his trial should continue because prosecutors had produced enough evidence.

The military says that 658 guerrillas had been killed since May 19 and some 1,400 others have been arrested or surrendered. Human rights groups said close to 300 civilians had been killed with another five added to the toll on Tuesday.