(Updates with Air Force statement)

By Teresa Cespedes

LIMA, Feb 28 (Reuters) - A Peruvian military helicopter carrying high-ranking army officers crashed in south-central Peru on Wednesday, killing three of the seven people aboard, an air force statement said.

The air force pilot, an army colonel and a retired army colonel were killed when the aircraft crashed in Anco district, in the Ayacucho region, 220 miles (350 km) southeast of the capital Lima, it said.

Also on board were an Ayacucho-based army general and colonel, and two additional air force crew members, it said. The statement did not specify if the survivors were hurt.

The air force aircraft, a Twin Bell 212, was on a mission to patrol a gas pipeline that snakes through the region. An investigation was under way to determine what caused the crash, according to the statement.

Once an epicenter of a fierce guerrilla insurgency, the Ayacucho region is now a front in the government's anti-narcotics campaign.

Earlier, an air force spokeswoman said the helicopter was carrying six members of the military, half of whom died in the crash, with the remainder being injured.

The air force identified the retired army colonel who died as an employee of pipeline company Transportadora de Gas del Peru (TGP), majority owned by Argentine companies Pluspetrol and Techint.

TGP pumps natural gas from southern Peru's Camisea field, the country's leading natural gas deposit, through the Andes to Lima on the Pacific coast.

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