A former Kazakh diplomat who for a time lived in Malta and who faced murder charges in Austria was found hanged in his cell in Vienna Tuesday in an apparent suicide, a prison official said.

Rakhat Aliyev was found Tuesday morning in the bathroom of his cell in Vienna's Josefstadt jail, prison director Peter Prechtl told the Austria Press Agency.

Aliyev, an estranged former son-in-law of Kazakh President Nursultan Nazarbayev, was charged in December over the kidnapping and killing of two bank managers in Kazakhstan. His trial had been expected to start in March or April. Aliyev had said he was innocent.

Aliyev, 52, was dismissed as Kazakh ambassador to Austria in 2007 after accusing Nazarbayev of totalitarianism.

He was sentenced in absentia to 40 years in jail in 2008 on charges including attempting to overthrow the government. He also was convicted in Kazakhstan of kidnapping the two bankers, who authorities there said were abducted in early 2007 after becoming embroiled in a commercial dispute with Aliyev. In 2011, Kazakh prosecutors charged him with murdering the bankers.

Austria rejected requests for his extradition to Kazakhstan but opened its own investigation.

Klaus Ainedter, a lawyer for Aliyev, said he had visited him on Monday and "there could be no talk at all of a danger of suicide."

"We trust that his death will be investigated very thoroughly and that the cause of death will be established clearly," he told APA.

Prechtl said officials had not considered Aliyev a suicide risk.

He was chief of Kazakhstan's tax police, deputy chief of the KNB state security service (Kazakhstan's successor to the Soviet, ambassador to Austria, and first vice foreign minister. While serving in those government posts, Aliyev amassed a fortune in the banking, oil refining, news media, telecommunications, and agricultural commodities sectors.

In February 2007 he was appointed to his second tour as Kazakhstan's ambassador to Austria, before being relieved of his post and losing his diplomatic immunity.

Until June 2007, Aliyev was married to Dariga Nazarbayeva, the eldest daughter of Kazakh President Nursultan Nazarbayev.

He later married Austrian citizen Elnasa Shorazova and enjoyed free movement throughout Europe although being investigated on fraud charges in the Austria, Germany and Malta. European Commissioner Cecilia Malmstrom told reporters that the investigation on fraud charges was difficult because of the different criminal legislation within the European Union countries.

After hiding in Malta to avoid an Interpol warrant for his arrest, and attempting to gain Cypriot citizenship, Aliyev was taken into custody in June 2014 by Austrian authorities on charges that include kidnapping and murder.

While in Malta, there were attempts for him to investigated on the alleged torture and frame-up of two Kazakh bodyguards in the late 1990s.

The former bodyguards filed a criminal complaint, calling on then-police commissioner John Rizzo and assistant commissioner Andrew Seychell, to investigate and prosecute Aliyev over the torture claims.

Their complaint was turned down in May 2013 with the police insisting that they do not have the jurisdiction over claims which took place in Kazakhstan in the late 1990s.