The group "is believed to have carried out numerous murders of government officials and leading police officers and their families from 2008" in North Ossetia, Austrian federal police said.
The alleged victims include the Russian republic's deputy vice-president, the deputy public prosecutor, a mayor and the chief of police, they said in a statement.
The gang's head, Aslan Gagiev, 43, who was arrested at Vienna's main train station on Saturday, allegedly personally shot dead at least six people in 2012-13 and seriously injured three others.
Gagiev fled abroad in 2013 and Interpol Moscow last December informed Austrian authorities that he might be living there, prompting local police to investigate.
Gagiev, who was using a forged Bulgarian passport, was "completely surprised" when he was arrested and did not resist. He will be extradited to Russia, the Austrian police said.