DAR ES SALAAM (Reuters) - Tanzanian authorities have launched a manhunt after poachers shot down a helicopter and its British pilot during an operation to track down elephant killers, officials said on Sunday.British pilot Roger Gower was tracking poachers on Friday in the Maswa Game Reserve when his helicopter was hit by an AK-47 rifle fired from the ground, Tanzania's tourism and natural resources minister, Jumanne Maghembe, said.

The mission had been a collaboration between the Friedkin Conservation Fund and the Tanzanian government, which has struggled to respond to what conservation groups say has been an explosion of "industrial-scale" poaching in recent years. "The government has launched a manhunt to find those responsible for this attack," Maghembe told reporters.

Dan Friedkin, chairman of the Friedkin Conservation Fund, said that Gower had been engaged in a coordinated effort with Tanzanian wildlife authorities to track down elephant poachers when his helicopter was shot down. He died in the crash.

"This tragic event again highlights the appalling risk and cost of protecting Tanzania's wildlife," Friedkin said in a statement.

A June census found that the elephant population in Tanzania, which depends heavily on its safari tourism industry, has declined from 110,000 in 2009 to a little over 43,000 in 2014.Demand for ivory from fast-growing Asian economies such as China and Vietnam, where it is turned into jewels and ornaments, has led to a rise in poaching across sub-Saharan Africa.Tanzanian authorities said they have made progress over the past months in their crackdown on illegal poaching.

Last October, it brought charges against a prominent Chinese businesswoman Yang Feng Glan, 66, dubbed the "Ivory Queen," for running a network that smuggled out tusks from 350 elephants.

Maghembe's deputy at the ministry, Ramo Makani, told Reuters that five suspects had been arrested since Gower's death and that the operation is still underway for the remaining suspects.

He also said that a second person who was travelling in the helicopter had survived the incident and is being treated for minor injuries and shock.

(Reporting by Fumbuka Ng'wanakilala; Editing by Edith Honan and Angus MacSwan)