Austria is seeking the extradition of a man arrested by Polish police who is suspected of involvement in the killing of a Chechen refugee in Vienna last month.
The man, arrested near Warsaw on February 19, is a Russian national of Chechen origin.
He is suspected of involvement in the killing of 27-year-old Umar Israilov, a former bodyguard of Chechen President Ramzan Kadyrov who was shot dead on January 13.
Israilov had filed a criminal complaint last year accusing Kadyrov of torture and other abuses in Chechnya.
Kadyrov's critics fear Israilov's death could effectively quash their best hopes for bringing conclusive evidence to light of alleged torture and other atrocities by the Chechen president.
Visita Ibragimov, the president of the Association of Democratic Chechens in Austria, told RFE/RL's North Caucasus Service that "we have several versions" of who killed Israilov.
Ibragimov said he hopes Austrian police "do everything to find the real murderer."
Kadyrov often has been accused of human rights abuses and of ruling Chechnya with an iron fist.