The arrest of a 31-year-old Chechen was carried out in a hotel near Warsaw, police said.
Israilov, 27, a Chechen who was seeking political asylum in Austria, was gunned down in Vienna's northern district of Floridsdorf on January 13 by two men, who shot him three times before fleeing the scene by car.
According to local media reports, Israilov was a former bodyguard for Chechen President Ramzan Kadyrov. In 2006, he fled to Austria where he claimed political asylum and in the same year, he took Russia to the European Court of Human Rights, accusing Kadyrov of systematic torture and kidnapping between 2003 and 2005 in order to control his opponents.
Israilov's father earlier made a public claim that his son has been persecuted and that the current Chechen president had personally tortured him in 2003 during a three-month prison term, after which Israilov was apparently forced to join Kadyrov's security forces.
According to a document distributed by Israilov's lawyer, Nadja Lorenz, Ramzan Kadyrov personally used a device to deliver electric shocks to him, as well as beating him.
Israilov's father also claimed that Russia had accused his son of terrorism and abduction and in 2007 sent an extradition request to the Austrian authorities. The request was rejected for lack of evidence.
The authorities in Chechnya have called the media speculation surrounding Israilov's murder "absurd."
