Witnesses helped police put together a sketch of one of the suspected killers
Police in Austria have arrested eight Chechens in connection with the murder of a ninth man, who was a critic of Chechnya's Moscow-backed leadership.
Elite commandos seized seven men in raids across the country on Wednesday. The eighth was detained just after Umar Israilov was shot two weeks ago.
The shooting of Mr Israilov, 27, in a busy street in Vienna as he returned from a shopping trip shocked Austrians.
Police said it was too early to establish a motive for the killing.
The seven men arrested on Wednesday are being investigated for conspiracy, aiding and abetting, and belonging to a criminal group, officials said.
Soon after the killing, Austria confirmed that Mr Israilov had repeatedly, and unsuccessfully, asked for police protection.
The dead man had accused Chechen President Ramzan Kadyrov, for whom he once worked as a bodyguard, of participating in kidnappings and torture.
When asked if his killing might have been politically motivated, Gerhard Jarosch, a spokesman for public prosecutors in Vienna, said "absolutely nothing could be excluded".
Mr Israilov, who had been granted asylum in Austria in 2007, was shot dead on 13 January in Vienna's Floridsdorf district.
Prosecutors showed a jacket thought to have been worn by one of the killers
He had tried to escape his killers, zigzagging across a crowded street, but stumbled as they fired four times, police said. When they caught up with him, he was shot twice in the head.
Witnesses to the murder noted the make and number-plate of the green Volvo getaway car, which police found a short time later in a nearby parking lot, the Austrian Times reports.
The car's owner, a Chechen refugee, was arrested hours later and is still in detention.
Hannes Gulnbrein, head of Austria's elite Cobra anti-terror squad, said that a jacket abandoned by one of the suspected killers had helped the investigation.
A total of 150 officers - 110 Cobra members plus 40 police officers - took part in coordinated raids on flats and asylum homes across Austria, starting at around 0600 (0500 GMT), he said.
Two bullet casings of the same 7.65 calibre as the murder weapon were found during the searches, Mr Gulnbrein said, describing the find as a "hot lead".
The raids lasted about four or five hours and none of those arrested put up any resistance and no-one was injured, he added.
The seven are being investigated for conspiracy, aiding and abetting, and belonging to a criminal group, Mr Gulnbrein said.
Austrian Interior Minister Maria Fekter has asked for an investigation into why no protection was offered to Mr Israilov.
An estimated 20,000 Chechens live in Austria, both legally and illegally.