Tanzanian authorities have arrested three suspects over the killing of a British helicopter pilot, who was shot down by AK-47 fire as he tried to stop poachers escaping with ivory they had taken from dead elephants.

Roger Gower was taking part in a helicopter operation to catch the gang in a game reserve next to Serengeti National park.

The poachers had already killed two elephants when Mr Gower, 37, saw a third elephant which had only just been slaughtered, said colleagues at the conservation group he was working for.

Roger Gower, 37, was killed after being shot while flying a helicopter over a Tanzanian game reserve

The vehicle crashed while it was tracking a group of elephant poachers near the Serengeti National Park

'They did see the two carcasses. While he was looking for the poachers, he heard gunshots and moved to the area and a saw a fresh carcass, the third elephant that had just gone down within 24 hours,' Pratik Patel, a close friend working on the same anti-poaching operation, told BBC Radio 5.

'I guess the poachers heard the helicopters searching and tried to make away with the ivory and hide.

'When Roger came across the carcasses, he hovered over them and moved forward to search the area. What he saw was evidence of ivory and turned the helicopter to come back to the spot.'

'At that point, one of the poachers sneaked out of the bushes and shot Roger, forcing the helicopter to hit the ground really hard.'

A second man who was in the helicopter with Mr Gower managed to bring it down, but at that point the man was really badly shot.

'The bullet that hit Roger cut through the floor of the helicopter, through his leg, part of his body and shoulder and hit his face, before going through the roof of the helicopter,' Patel said.

'It was from a heavy calibre gun – probably the same gun that they used to kill the elephant.'

Tanzanian minister Jumanne Maghembe announced the arrests and pledged that any other suspects will be caught in security operations after the attack in Maswa wildlife reserve.

Lazaro Nyalandu, a former minister of tourism and natural resources, wrote on Twitter that Gower was killed by AK-47 assault rifle fire.

'You loved our country and I knew you on many flights we took together,' Nyalandu wrote.

Shocking pictures were posted on Facebook last night including this one of the pilot's blood-stained chair

Mr Gower, who trained as an accountant, was working with the Friedkin Conservation Fund in Tanzania

Patel paid tribute to 'a great guy, a great friend, a great pilot' who he said had loved working with Tanzania's wildlife.

Last night, shocking pictures of the helicopter were posted on Facebook. They showed several bullet holes, including one through Mr Gower's bloodstained seat.

Dan Friedkin, chairman of the Friedkin Conservation Fund, who Mr Gower was working with, released a statement last night saying: 'On Friday, we lost our colleague Roger Gower who was killed in the fight against elephant poaching in Tanzania.

'We are profoundly saddened by the loss of our dear friend. This tragic event again highlights the appalling risk and cost of protecting Tanzania's wildlife.'

Mr Gower trained as an accountant in London and became a helicopter pilot in 2004. Before working in Tanzania, he flew from neighbouring Kenya, working for safaris and excursions.

The Foreign Office said: 'We are providing assistance to the family at this difficult time.'

The Foreign Office has confirmed it is providing support to the victim's family

Maswa, the park where Gower was operating, lies on the southwest boundary of Serengeti.

The region’s massive wildebeest migration passes through Maswa in January and February, according to the Friedkin Conservation Fund.

The park’s rangers encounter poachers on a regular basis, it said.