JAKARTA, May 15, Reuter - Indonesian soldiers publicly executed alleged separatist rebels in the northern province of Aceh, shooting them without trial, an eyewitness said.

"On Saturday night (May 4) they shot five people in public in Sigli in front of everyone. I saw it with my own eyes," said a prominent resident of the northern Aceh town at the centre of an 18-month-old separatist rebellion.

Armed forces spokesman Nurhadi Purwosaputro told Reuters on Tuesday night he knew of no extra-judicial public executions.

"But even they (the rebels) have a right to a legal process. If it did happen without due process of law, we will certainly deal with everyone involved very severely indeed," he said.

Nurhadi said armed forces commader Try Sutrisno, recognising major disciplinary problems in some parts of the army, had ordered that any soldiers who broke the rules be dismissed.

The witness said the public killings began at dusk and took place in various parts of the town, such as a clearing behind the regional development bank.

He saw one shooting and, walking around Sigli, counted four more fresh corpses which other witnesses said had also been shot publicly.

A local official in the town told Reuters by phone that those killed had been arrested by the army.

"You have to understand, they were rebels, they were in the wrong," he said.

Intellectuals and a diplomat who received similar reports from aid workers in the area confirmed they knew of the executions, although they said details were hazy.

The strongly Islamic province of Aceh at the northern tip of Sumatra has a long history of rebellion, first against Dutch colonialists and later against Jakarta's rule.

Residents of the province have for months spoken of finding corpses dumped on the roadside in the mornings, apparently shot by the military during nightly curfews imposed in many areas.

Special forces in the area say they kill only rebels in their operations, but a local official told Reuters recently that about a third of the victims could be innocent. Locals say the killing has become more or less indiscriminate.

Observers who keep a close count of deaths say at least 2,300 civilans, rebels and soldiers have died since the military began a campaign to wipe out the separatists, whose main targets are troops and Javanese migrants in the gas-rich province.

The rebels appear to be a loose coalition of vengeful ex-soldiers fired for indiscipline, common criminals and committed separatists who want to end Jakarta's rule.

The alleged public executions have shocked even human rights workers and diplomats who have for months acknowledged widespread extra-judicial killings, mainly of civilians.

"I just don't want to believe it's true. They used to say we shot these people resisting arrest, we shot them so they didn't shoot us first. But now they have given up all pretence," said one human rights worker.

Villagers in the Pidie region of which Sigli is capital must have written permission from security forces if they want to leave their district, a local official said.

And after Acehnese started leaving for neighbouring Malaysia in boats, saying they were fleeing fighting between the government and rebels, fishermen whose families had made a living off the sea for generations were forbidden to take out their boats.