Jakarta – Indonesia has captured provocateurs, some of them formerly with the military, who were trying to stir up trouble in rebellious Aceh province, senior minister and former armed forces chief General Wiranto said on Monday.

"We have captured provocateurs in relation to cases in Aceh. They are thugs who come from Medan and there are also some former rouge elements in the military," Wiranto, coordinating minister for political and security affairs, told reporters.

Medan is the capital city of North Sumatra, a territory adjacent to Aceh. Calls to break away from Indonesia are mounting in Aceh. Shadowy provocateurs are often blamed in Indonesia for stirring up trouble when unrest breaks out.

On Saturday, Aceh celebrated the 23rd anniversary of the founding of its rebel guerrilla movement. Fears of widespread unrest at the weekend were not realised, but several incidents in which security forces fired at protesters left one person dead and several injured, witnesses said.

National police chief General Roesmanhadi said on Monday that police only fired in self-defence. "There was some shooting but ... the Indonesian police were not the ones who started it," Roesmanhadi told reporters. He added that some people in the crowds had pointed weapons at the police and had ignored warning shots.

The situation in Aceh on Monday was calm and most businesses and public offices in major cities had resumed normal operations, residents said.

The official Antara news agency reported that Indonesia's military had sent six warships to the waters off Aceh in a bid to strengthen security.

It quoted the chief of Indonesia's navy, Rear Admiral Adi Haryono, as saying the move was also to prevent the smuggling of weapons into the province. Aceh lies on the northern tip of Sumatra island and serves as an entrance to the busy international shipping lanes of the Straits of Malacca.