It said Bestari Raden, 55, was said to be undergoing intensive interrogation.

"Torture and ill-treatment are routine in military custody in (Aceh) and there are serious concerns for his safety," the London-based rights group said in a statement.

The military, which is in the 10th month of a campaign against separatist guerrillas, says Raden was arrested for alleged links to the rebels.

Fellow activists say he was arrested because he opposes a controversial highway project advocated by the Aceh governor and President Megawati Sukarnoputri.

Amnesty said that on the morning before his arrest Raden had visited the region in his capacity as a member of a government team to review the Ladia Galaska highway project.

It said there was concern he may not be a member of the Free Aceh Movement (GAM) as the military alleges, "but has been detained because of his activities in opposing government policies in (Aceh)."

Amnesty said Indonesian troops and police "have carried out grave human rights violations" during a 27-year war against the rebels. GAM has also been responsible for human rights abuses, it said.

Environment Minister Nabiel Makarim is among those opposed to the proposed road network through a huge conservation area in Aceh and North Sumatra. He says it could worsen illegal logging and lead to the destruction of the forest and its ecosystem.

The European Union, which has funded the conservation area, has also expressed alarm.

TERRA.WIRE