A Peruvian air force plane with 20 people on board crashed in Peru's northeastern jungle in a rainstorm, but at least eight survived, officials said Friday.

The plane, a Twin Otter, was declared missing Thursday evening after leaving Orellana, about 580 kilometres northeast of Lima, Peru's Defence Ministry said in a news release.

Defence Minister Allan Wagner said at least eight survivors had been rescued Friday.

"The information that I have is that a police helicopter reached a site near where the plane was found and found a survivor," Wagner said. "A marine patrol, by land, found seven other survivors."

He said the twin-engine plane was located in a low, jungle-covered mountain range about 20 kilometres from Orellana.

Wagner declined to confirm the number of people aboard, although regional officials and the air force said there were 17 passengers plus a three-man air force crew.

Julio Barrientos, a government prosecutor in the Ucayali region, where the plane went down, told Lima's top radio news station, Radioprogramas, that rescue helicopters spotted a fire set by the survivors in a jungle clearing.

The plane was part of the air force's civic action flights connecting small communities in the jungle not served by commercial airliners.

The Defence Ministry press release said the plane lost radio contact with airports at 5:45 p.m. local time on its flight between Orellana and Contamana. The plane was scheduled to make five stops, ending in Pucallpa, a city 490 kilometres northeast of Lima.

It was raining heavily at the time of the accident, said Norman Lewis del Alcazar, vice-president of the Loreto region, the area where the flight originated.

Loreto President Ivan Vasquez complained that the air force planes used in the civic action flights are old. He said the regional government has an agreement with the air force to provide fuel for the flights "to reduce the cost of the tickets so that poor people can travel in emergencies."

There are few roads in the vast northeastern jungle of Peru, and other than river travel, which can take days, the flights are the only way to reach distant points.