By Alister Doyle

OSLO (Reuters) - The Philippine government and Maoist-led guerrillas opened peace talks in Oslo on Monday, seeking to end nearly five decades of conflict that has killed more than 40,000 people.

Both sides announced ceasefires at the weekend to buoy the Oslo talks, the first formal meeting in five years in fitful peace talks dating back to 1986 over one the world's longest-running guerrilla insurgencies.

The rebels praised new President Rodrigo Duterte for steps including the release of 17 prisoners to attend the five-day meeting in Norway and the appointment of what they called progressives to cabinet posts including agrarian reform.

"Duterte has shown magnanimity and generosity," Jose Maria Sison, the exiled founder of the Communist Party who lives in the Netherlands, told an opening ceremony.

The two delegations shook hands, gave "V" for victory signs with their fingers and smiled at the start of the talks between the government and the National Democratic Front (NDF), the political arm of the Communist Party.

Six negotiators from each side faced each other in the Holmenkollen Park Hotel's "Nobel" room, named after the Nobel Peace Prize, with photographs of winners including the Dalai Lama and Holocaust survivor Eli Wiesel on the walls.

Duterte wants to end guerrilla wars with both communist and Muslim rebels that have been hampering economic development. The 3,000-strong New People's Army, the armed wing of the communist party, operates mainly in the east and south.

The government delegation said its ambition was to complete peace talks within a year, despite frequent past failures over rebel demands that include "revolutionary changes" such as nationalizations of industry and redistribution of land.

"We have imposed a timeline of nine to 12 months," said Silvestre Bello, the labor minister and chair of the government team.

Bello's counterpart on the rebels' side, Luis Jalandoni, told Reuters that a year was "optimistic" given the huge differences. Still, he said it was likely that the communists would extend the ceasefire if the Oslo talks go well.

Norwegian Foreign Minister Boerge Brende told the meeting that there seemed a "historic momentum" building to end the conflict. "I'm really crossing my fingers," he said.

In a previous setback, Duterte had ended a unilateral truce with the communist New People's Army late last month as rebels did not respond to a deadline to reciprocate the government's truce.

Benito and Wilma Tiamzon, a rebel couple released from more than two years in jail to attend the meeting, expressed hopes of a long-lasting amnesty. They told Reuters they would return to the Philippines after a visit to the Netherlands.

(Editing by Andrew Heavens and Dominic Evans)