Two hundred machete-wielding villagers in Lhok Nibung, eastern Aceh, stopped a bus on Tuesday and pulled 16 soldiers off.

Several of the soldiers escaped by showing civilian identification papers but seven of their comrades were dragged away, attacked and tortured and their bodies then dumped in a river.

In another outbreak of violence on Wednesday, soldiers fired warning shots over a mob of about a thousand people which had set fire to a police station and attacked a military post near the industrial town of Lhokseumawe. No injuries or arrests were reported.

Dislike of the security forces follows years of suppression

The armed forces were quick to place blame for the killings. "There are indications that the Acehnese separatist movement is behind this attack," said Major-General Syamsul Ma'arif.

Three hundred extra troops have been deployed in the area to keep order, and also to track down those responsible for the killings. The security forces arrested 25 suspected separatist rebels.

The separatists are campaigning to free the deeply Islamic province, on the northern tip of Sumatra island, from the control of the government in Jakarta.

General Wiranto: killings could affect moves to put security in hands of community

A low-level separatist insurgency has simmered in Aceh for years. Correspondents say a nine-year army crackdown against the rebels involved widespread army atrocities, torture, rape and the dumping of victims in mass graves.

The military has acknowledged that 760 people died in fighting in the late 1980s, although human rights groups put the toll much higher. A team from Indonesia's official human rights commission dug at several suspected grave sites in August, unearthing the bones of scores of victims.

Simon Ingram describes the latest incidents in Aceh

Following the resignation in May of President Suharto Indonesia's armed forces apologised for previous atrocities and said they were withdrawing all combat troops.

A riot erupted in the town of Lhokseumawe in August after the final batch of combat troops was withdrawn.

Military rethink

General Wiranto, the chief of the Indonesia's armed forces, said Tuesday's attack could affect a plan to put security in the hands of community leaders: "The killing was a brutal action which can never be tolerated by the armed forces," Wiranto said. "This action could spoil the wishes of the Aceh people to free the region of military operations."

Poverty seen by some as the common cause for Indonesian violence

BBC South East Asia Correspondent Simon Ingram says that whatever the motive for the attack, it will serve to deepen concerns over the wave of violent incidents stemming from a range of often unconnected causes that is currently sweeping Indonesia.

The Jakarta Post newspaper has also commented on Indonesia's "appalling" increase in violence cruelty and anger. "The painful reality," it said in an editorial, is "that the majority of our people are suffering from economic hardships."