Rakhat Aliyev, the Kazakh president’s former son-in-law turned political enemy, has been found dead in an Austrian jail as a result of suicide, a court spokeswoman has said.

Aliyev’s lawyers, however, say they doubted he had killed himself.

He had been awaiting trial for the alleged murder of two bankers in Kazakhstan after Austria refused extradition

because of the former Soviet republic’s human rights record.

A former Kazakh ambassador to Austria, Aliyev became a vocal critic of his country’s president, Nursultan Nazarbayev, and had denounced the case against him as politically motivated.

He had been in custody since June when he turned himself in to Austrian authorities after a four-year investigation.

The Austria Press Agency (APA) quoted the corrections department director, Peter Prechtl, as saying Aliyev’s body had been found at 7.20am (0620 GMT) in a cell of Vienna’s Josefstadt prison, where he had been in solitary confinement.

He had hanged himself, Prechtl said.

Agence France-Presse reported that Aliyev had been due to testify on Tuesday in the trial of two inmates who he alleged had threatened to kill him and make it look like a suicide unless he paid them.

Defence lawyers Manfred and Klaus Ainedter were quoted by APA as saying they could not imagine their client, 52, had killed himself.

“I have significant doubts about this, without wanting to blame anyone. I visited him yesterday. There could be no talk whatsoever of danger of suicide,” Klaus Ainedter said, adding that he expected a thorough investigation.

Prechtl told APA that Aliyev had requested a single cell in the prison’s hospital unit. He was not considered at risk of suicide and was graded “green” in the corrections department system, which meant he could be left unattended.