Indonesia and Aceh rebels on Monday signed a peace treaty to end nearly 30 years of fighting that killed 15,000 people, but rebel leaders voiced concern about government troops remaining in the region.

The signing ceremony in Helsinki followed seven months of talks mediated by former Finnish President Martti Ahtisaari (search), who spurred the two sides to agreement to help international aid reach Aceh province, which was devastated by last year's tsunami.

The pact gives amnesty to members of the Free Aceh Movement (search), or GAM, and allows the region limited self-government.

It was signed by Indonesian Justice and Human Rights Minister Hamid Awaluddin (search) and Malik Mahmud (search), an exiled rebel leader who was briefly jailed in Sweden last year after Indonesia accused him of terrorism.

Both sides also agreed to end hostilities immediately after the signing.

In Aceh province, thousands of people gathered at the region's largest mosque to witness the televised signing. The crowd clapped and shouted as the Indonesian government inked the deal, but the celebration was remarkably subdued.

"All we want is peace," said Nassruddin, a high school physics teacher who goes by one name. "A few years ago we teachers were targeted by the rebels. They burned a lot of schools. We were always scared."

The accord became possible after GAM agreed to renounce a demand for full independence and disarm, and the Indonesian government said it will cut troops in the region, from 35,000 to 14,700, and police from 15,000 to 9,100.

Mahmud, however, said that too many troops will remain.

"At the end of the process there will be around twice as many troops to be stationed in Aceh as any other [part] of Indonesia," he said, after signing the pact.

He also accused the government of denying the existence of anti-GAM militias in the province, which humanitarian organizations allege attacked civilians.

"We know that many militia organizations do exist in Aceh, and that they are directly linked to and supported by the Indonesian army," Mahmud said. "Militia members have recently been saying that after GAM is disarmed they will kill GAM members."

"If GAM defends itself against these militias, this will be the excuse the [military] is looking for to relaunch military operations," he added.

Ahtisaari was upbeat about the treaty.

"This is a beginning of a new era for Aceh. Much hard work lies ahead," he said, after shaking hands with the signatories. "It is of utmost importance that the parties honor the commitments they have made in the agreement."

The treaty stipulates that a new law on governing Aceh will come into force by March 2006, allowing the province to retain 70 percent of the province's revenue from oil and gas.

The peace process was initiated by Ahtisaari, a former peace broker in the Balkans and Namibia, after he was approached by the Indonesian government to help find a solution to the conflict.

GAM leaders, who have been living in exile in neighboring Sweden for decades, also backed the choice of Ahtisaari and joined in the talks that were held at a secluded manor house outside the Finnish capital.

After the tsunami, which killed 130,000 people in Aceh alone, aid workers poured into the formerly closed province, leading to international pressure on Jakarta to halt the violence — particularly from the United States and the European Union.

A previous truce ended after only six months in 2003, when the Indonesian army expelled foreign observers, declared martial law, arrested rebel negotiators and mounted an offensive in which more than 3,000 people died.

Hostilities in the area broke out in 1976. Although many Acehnese wanted an end to the bloodshed, there was general support for independence because of abuses. Human rights groups accuse Indonesia's army of executions, disappearances, torture and rapes.