Vienna  - Three human rights organizations said Friday they were "deeply alarmed" about the killing in Vienna of a Chechen refugee who had filed human rights complaints against Chechnya's leadership.

Police are searching for two unknown men in the shooting of Umar Israilov, 27, near his Vienna home on Tuesday.

The victim's father, Ali Israilov, said his son had unsuccessfully asked for Austrian police protection and that Umar Israilov had been told of a death list containing the names of 50 Chechens exiles in Austria.

"The Austrian government should act swiftly to bring to justice those responsible for the killing of a Chechen man who had alleged he had been tortured by Ramzan Kadyrov, who is now the Chechen president," Human Rights Watch, Amnesty International and the Memorial Human Rights Centre said in a joint statement.

Last December, the younger Israilov felt threatened by an unknown Chechen man and asked police for help, his father said Friday in a statement. "I deeply regret that Austrian police did not become active," said the father, who also lives as a refugee in Europe.

Umar Israilov was a Chechen resistance fighter who was captured in 2003 and tortured by security forces commanded by Kadyrov, according to his father. The younger Israilov was subsequently forced to work in Kadyrov's security detail, but managed to flee Chechnya in 2004.

The victim's father said he and his son had brought legal cases before state prosecutors in Russia and before the European Court for Human Rights in Strasbourg.

The elder Israilov alleged that a Chechen man appeared in Vienna in June 2008 to try to convince the former rebel to return home with a mix of charms and threats.

"He said that he had seen in Kadyrov's residence a list with names of 300 Chechens who 'have to die,' and around 50 of them were in Austria," Ali Israilov said of his son's visitor.

Before this incident, Russia had tried, without success, to have Umar Israilov extradited from Austria on terrorism charges.

An official of Vienna's police intelligence agency said Thursday that although his organization had known about Israilov's security concerns, the refugee had never asked for police protection.

However, security measures have now been put in place for Israilov's wife and his three children, Walter Nevoral of the Vienna police said. (dpa)