Rakhat Aliyev, a former ambassador to Austria, was arrested in Vienna at the beginning of June after Kazakh authorities accused him of kidnapping two top managers of Nurbank, a bank he controls in Kazakhstan.
Aliyev said the charges against him were trumped up by President Nursultan Nazarbayev, who considered him a political threat.
On August 7, an Austrian court rejected a request from Kazakhstan to extradite Aliyev, saying he could not receive a fair trial in Kazakhstan.
"The Interior Ministry entirely disagrees with the Vienna court's decision to refuse the extradition of Kazakh nationals, including Rakhat Aliyev," Bagdat Kozhahmetov said.
He also called the decision inconsistent, saying that it "discredited the international legal environment" and was not within the framework of international legal practice.
"The court's biased decision, refusing to extradite Rakhat Aliyev and his accomplices, accused of the abduction of three persons, is clearly politically-motivated," he said.
The spokesman added that Kazakh investigators had irrefutable evidence that the bank officials had been kidnapped by suspects under Aliyev's guidance.
Soon after the court's announcement, the spokesman criticized the hearings, saying none of the lawyers hired by Kazakh authorities were present in court, and none of them had even been informed of the time and place of the trial.
Explaining the Vienna court's ruling, prosecutor's spokesman Gerhard Jarosch said: "The court ruled that his human rights could not be guaranteed if he were sent back home." The spokesman said the decision implied Aliyev was now a free man.
Aliyev, the former husband of Nazarbayev's eldest daughter Dariga, was fired as Kazakhstan's ambassador to Austria May 26 after he accused the Kazakh president of totalitarian rule and announced he would run against the leader in the 2012 elections. Weeks later, the president's daughter divorced him.
Nazerbayev, who has ruled the large ex-Soviet state for 17 years, recently signed a constitutional amendment allowing him to be re-elected an unlimited number of times, a rule that will not apply to subsequent leaders.
Despite criticism of his autocratic style of leadership, he remains popular in his home country, which has seen strong oil-driven economic growth in recent years.
Rakhat Aliyev, 44, told Austrian authorities that if he were sent back to Kazakhstan, his life would be in danger. As well as the kidnapping charge, he is accused in Kazakhstan of organizing a group of raiders who illegally seized land and real estate.
