Indonesia signed a peace agreement Monday with rebels in Aceh province who have fought for nearly 30 years for a separate state, lending a crucial boost to efforts at rebuilding the tsunami-battered region.

Under the accord, signed at a ceremony in Helsinki, the Finnish capital, the Free Aceh Movement set aside its long-standing demand for independence and agreed to immediately begin turning over its weapons to international observers, drawn mainly from the European Union. Disarmament is due to be completed by the end of the year.

In return, the Indonesian government agreed to revise electoral laws so that Acehnese can form local political parties and nominate candidates for offices at all levels of government. Indonesia will also significantly scale back its security force in Aceh, estimated at 35,000 soldiers and police officers. The government also agreed to notify observers before staging any military maneuver involving more than a platoon.

"There is always a time for rain to stop, and there is always a time for war or conflict to end," said Indonesia's justice minister, Hamid Awaluddin, who led the government's delegation in Helsinki.

The agreement capped five rounds of talks mediated by Finland's former president, Martti Ahtisaari.

Previous deals to end one of the world's longest-running civil wars, including an agreement signed nearly three years ago, collapsed in part because of resistance from members of the Indonesian military, who were determined to end the conflict by force. Up to 15,000 people are estimated to have died as a result of the fighting in Aceh, many of them civilians.

The new accord, however, has unprecedented support from the Indonesian government. Efforts to negotiate a settlement were largely initiated by President Susilo Bambang Yudhoyono, a retired general elected last year, and, in particular, the influential vice president, Jusuf Kalla, who secretly initiated contacts with the Aceh rebels shortly after the leaders took office.

Moreover, the separatist movement, known by its Indonesian initials GAM, demonstrated willingness to compromise after government forces battered the rebel ranks during a two-year offensive.

But both sides acknowledged that the turning point was the massive Dec. 26 tsunami, which killed at least 150,000 people in Aceh, on the northwestern tip of Sumatra island. With much of the province in ruins and foreign governments offering hundreds of millions of dollars in aid, Indonesian and rebel leaders decided to set aside the conflict for the sake of reconstruction.

"It is a leap of faith GAM has taken to allow Aceh to rebuild after the devastating tsunami, which killed so many of our brothers and sisters," said Malik Mahmud, the chief rebel negotiator. "And it is a leap of faith that GAM has taken to give the people of Aceh their opportunity to build a better and brighter future for themselves, their children and generations to come."

Included in the pact is a series of enticements for the rebels, such as a pledge to provide former fighters with farmland carved from the holdings of a government plantation company, and an offer of amnesty to those now imprisoned. Rebels convicted of criminal offenses will not be released.

Negotiators also agreed that Aceh will be entitled to receive 70 percent of revenues from the province's oil and gas reserves. The province will write many of its own laws and have its own flag, crest and anthem.

But GAM negotiators said that the most important political concessions were those allowing the Acehnese to form political parties to represent and promote local interests.

"The only way to ensure peace in Aceh is through the implementation of a genuine democracy," Mahmud said.

Speaking to the delegations by videoconference from Jakarta, Yudhoyono gave special thanks to GAM's negotiating team.

"We certainly hope that this is the era, a great era for us to really bring peace in Aceh, to be reunited, to work together in a very democratic atmosphere for a better future," the president said.

Negotiations between Indonesian Justice Minister Hamid Awaluddin, left, and the Free Aceh Movement's chairman, Malik Mahmud, right, were guided in Helsinki by Finland's former president, Martti Ahtisaari.