A British headteacher murdered while canoeing along the Amazon was tortured and sexually assaulted by a gang before being killed and dumped in the river, it has been claimed.

Horrific new details of the last moments of Emma Kelty's life were revealed in a confession made by one of the suspects shortly after the British kayaker's death.

Evanilson Gomes da Costa was found dead after going on the run in the wake of the murder having reportedly been shot by rival drug traffickers.

But before he died - and just hours after the death of Miss Kelty - the 24-year-old told a local villager what the gang had done, it has been claimed.

One of the men, Artur Gomes da Silva, claimed he tried to decapitate the headteacher with a machete. José Afonso Barradas Jr, police chief in the city of Coari, northwestern Brazil, said: 'He claimed he tried to cut her head off with a machete but failed.' 

The villager said da Costa had told him how his gang had come across Miss Kelty's tent and, believing it to belong to drug traffickers, had opened fire from 50m away.

The unnamed villager added: 'The woman was hit in the arm. She started waving frantically and screaming for help.'

But still believing she was transporting drugs, they approached the tent and started attacking her, cutting off her hair with a knife as they ordered to hand over narcotics. One of the group then slit her throat before all four men 'sexually abused her', the villager said.

Her body was then dumped in the Amazon before the men fled. Villagers provided police with their details and identities, he added.

It comes after it emerged that a man  arrested over the murder has admitted to slitting her throat and throwing her bullet-riddled body into a river, police say.

Da Silva made his confession after being held following an anonymous tip-off, police chief Jose Barradas revealed.

The suspect was found hiding in bushes with a phone and a GPS tracker after the 43-year-old former headmistress was murdered.

His confession comes as it emerged the killers alerted authorities to their crime after unwittingly triggering a distress signal on her equipment. Investigators had first thought the emergency alert which pinpointed Emma Kelty's exact location and triggered a search operation by Brazil's Navy had been sent by the victim herself.

But in fact the 'SOS' button was pressed by one of her killers who was trying to work out how to use the device they had stolen, an hour and a half after her death.

Police have now recovered the GPS device, as well as a mobile phone and a memory card.

The GPS signal sent at 10pm last Wednesday night led investigators to the riverside village of Lauro Sodre, 150 miles west of Manaus, and a manhunt which has brought about the arrest of three men accused of her murder. One of the suspects, Artur Gomes da Silva, nicknamed Beira, was due to be flown from Coari to Amazonas state capital Manaus today and remanded in prison ahead of trial.

Mr Barradas, insisting Miss Kelty had not been decapitated as was initially reported, said: 'It was an easy arrest. He confessed that after the British tourist's shooting, he and another suspect slit her throat and then threw her body into the river.'

Yesterday Barradas said he doubted anyone would have discovered what happened to Ms Kelty if the 'stupid' gangsters hadn't set off her emergency locator by mistake.

He said: 'They didn't know how it worked, so were messing around with it and pushing buttons.

'One of them must have pushed the button which transmitted an alert that she was in trouble. In turn the company that received it alerted the Navy, along with the exact location of where the button was pushed.

'Without that, it would have been very difficult to know where in this vast area of jungle she had gone missing.

'It would have probably remained an unsolved mystery and her killers never brought to justice.