The Philippine government and Maoist rebels have signed an indefinite ceasefire deal to facilitate peace talks aimed at ending one of Asia's longest-running insurgencies.

"This is a historic and unprecedented event ... [but] there is still a lot of work to be done ahead," President Rodrigo Duterte's peace adviser Jesus Dureza said at Friday's signing ceremony in Norway, which is mediating the talks.

READ MORE: Philippines and communist rebels agree on ceasefire

Both sides agreed to implement unilateral, indefinite ceasefires - something that has never been achieved before in the peace process.

Norwegian Foreign Minister Borge Brende described the agreement as a "major breakthrough".

"We are on the highway to peace and we are talking of a timeline of maximum 12 months," Silvestre Bello, the Philippine government delegation's head of negotiations, told AFP.

The two parties have been meeting in Oslo since Monday, wrapping up their talks with the signing ceremony on Friday.

As a prelude to the negotiations, both sides had agreed to a ceasefire, but the truce commitment by the Communist side was due to end on Saturday.

The two parties also agreed to "speed up the peace process, and aim to reach the first substantial agreement on economic and social reforms within six months," a statement from the Norwegian foreign ministry said.

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"They plan to follow this up with an agreement on political and constitutional reforms, before a final agreement on ending the armed conflict can be signed."

The two delegations agreed to meet again in Oslo on October 8-12.

Philippine President Duterte himself hailed the progress made in Norway.

"We are in a better position [to talk peace] now. There is a window," he said, adding: "We are not fighting the Communists. They have declared a truce. In return, I also ordered a ceasefire."

'Good atmosphere'

The head of the rebel delegation, Luis Jalandoni, was optimistic about the potential for achieving a lasting peace deal.

"We think that the peace talks now can move forward with a good atmosphere and try to move on with the [negotiations on] social and economic reforms, which are vital for addressing the roots of the armed conflict," he told AFP.

The government and the rebels also renewed an agreement that ensures immunity and security for key representatives of the rebels' political wing, the National Democratic Front, so that they can take part in the negotiations.

The Communist Party of the Philippines launched a rebellion in 1968 that has so far claimed the lives of more than 30,000 people, according to official estimates.

Its armed faction, the New People's Army (NPA), is now believed to have fewer than 4,000 gunmen, down from a peak of 26,000 in the 1980s, when a bloodless revolt ended the 20-year dictatorship of late president Ferdinand Marcos.

They remain particularly active in rural areas, where they are notorious for extorting money from local businesses. They also regularly attack police and military forces, sometimes targeting them in urban areas.

In 2002, the US State Department designated the Communist Party and the NPA as terrorist organisations.

Forging peace with the rebels has been the elusive goal of Philippine presidents since a 1986 revolution that toppled dictator Ferdinand Marcos.

The force behind the current talks is President Duterte, who took office on June 30 after a landslide election victory.

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On Monday, his government said it hoped to reach a peace accord within a year.

Duterte, who calls himself a Socialist, hails from Mindanao, the impoverished southern third of the Philippines where two rebellions - Communist and Muslim - have been most active.

He says ending both insurgencies is vital to his plan to curb poverty. He has even sketched the possibility of forming a coalition government with the rebels.

Duterte reputedly has close links to the Communists and is a former university student of Jose Maria Sison, now aged 77, who established the party.

The two sides hope to breathe new life into the process by discussing the outstanding issues of social and economic reforms, political and constitutional changes, and an end to hostilities.

Previous peace talks have addressed one issue at a time.