Separatist rebels in Indonesia's Aceh province have released 18 civilians they abducted late last month, a source involved in arranging the release said.

"They were released yesterday afternoon," the source, who spoke on condition of anonymity, told AFP Friday, adding they are in good condition.

The victims, nine crewmen seized from an oil company supply ship and nine athletes and sports officials, were freed by the Free Aceh Movement (GAM) from their hideout at a remote location in East Aceh, he said. They were taken immediately to Medan, the capital of neighbouring North Sumatra province.

GAM, in a statement issued by its exiled leadership in Sweden on Thursday, said the 18 would be released immediately after they were found to be civilians and not involved in military operations.

The nine crewmen were seized Sunday from a vessel headed for an oil exploration field off North Aceh. The rebels previously denied involvement.

The seven athletes and two sports officials were abducted in the province on June 26 while returning from competing in the Aceh Games. Previous reports said nine athletes and two sports officials were missing.

GAM blamed the detention of the 18 on what it called the military's "massive" operations in the province.

The rebels said the 18 were stopped and questioned. "When it was discovered that they were non-residents of the area, we were – for security reasons – forced to detain them to ascertain who they are and what they were doing in the area.

"Having determined that they were innocent civilians and in no way involved in military operations, they are released forthwith." GAM said it has ordered field commanders not to harm civilians or civilian infrastructure including schools. The army accuses the rebels of responsibility for torching a string of schools and of toppling power pylons.

The Indonesian government, citing what it called a series of kidnappings and murders by the rebels, announced Thursday it plans to declare a state of civil emergency in the province if parliament approves the proposal.

Rebel spokesman could not be reached for comment on the plan announced by top security minister Susilo Bambang Yudhoyono.

Yudhoyono described the rebels as "terrorists." He added: "It is our duty to tell the international community – enough is enough. We have given them (rebels) chances but it turns out like this." GAM has been fighting since 1976 for an independent state in the province. An estimated 10,000 people have been killed since then, 600 of them this year alone.