Shining Path rebels have kidnapped dozens of workers in Peru's natural gas industry before letting most of them go hours later in a remote jungle, officials and local radio said.

At least 23 of 30 hostages have been freed, RPP radio said on Monday. Most kidnap victims were employees of the Swedish firm Skanska, which services a natural gas pipeline in southeastern Peru, officials said.

President Ollanta Humala, a former military officer, has vowed to capture remnant bands of Shining Path rebels that went into Peru's thriving cocaine trade after the Maoist founders of the insurgency were imprisoned in the early 1990s.

"Shining Path rebels took them hostage early this morning in the village of Kepashiato," an official from the pipeline company said. "They took them from the hotel where they were sleeping."

Neither the government nor Skanska has said whether they had intervened to free some of the workers.

The South American country is the world's largest cocaine exporter and the rebels control drug trafficking routes in two prime coca-growing regions: the Huallaga Valley in central Peru, and the Ene and Apurimac valleys (VRAE) in southeastern Peru.

More than 50 soldiers and police have died in the last three years trying to catch Shining Path fighters.

In February, in the Huallaga Valley, the government caught Artemio, the nom de guerre of Shining Path leader Florindo Eleuterio Flores. He was the last high-ranking figure from the historical core of the insurgency still at large.

It was a major victory for Humala, who fought the group while in the army in the 1990s.

After Artemio's arrest, the government said it would go after rebels in the VRAE, where they are led by Victor Quispe.

A high-ranking military official said the army was closing in on a group of rebels at the time of Monday's kidnapping.

"They took the hostages to halt our advance," the military official said.

A resident of Kepashiato told RPP radio that 150 armed insurgents were in the area and about 80 of them carried out the kidnapping.

It was the first large kidnapping by the rebels since 2003 but had no impact on natural gas supplies.

Owners of the pipeline company TGP, which carries gas from Peru's Camisea gas fields, include Argentina's Pluspetrol, US-based Hunt Oil, South Korea's SK Energy and Suez-Tractebel, among others.