Advocate Antoine Sollacaro was the most high profile victim of a spate of killings that has been linked to feuds between rival criminal gangs linked to sections of the Corsican nationalist movement.
Four of the suspects were arrested in Ajaccio, the island's capital, and two others, including a police official, were detained in Marseille on the French mainland.
Sollacaro died in an execution-style hit at a petrol station in Ajaccio on October 16th. He was one of at least 25 victims of unexplained murders on the island since the start of last year.
A former chair of the Corsican bar, the 63-year-old Sollacaro was best known for having defended Yvan Colonna, the nationalist currently serving a life sentence for the 1998 assassination of France's top official on the island, the prefect Claude Erignac.
Sollacaro's slaying prompted French Prime Minister Jean-Marc Ayrault to promise an increase in the police resources dedicated to stemming violence on Corsica.