Three Kurdish women activists have been found dead with gunshot wounds to the head in the Kurdish Institute of Paris, reports the BBC.
One of the women is said to be a co-founder of the militant Kurdish separatist movement, the PKK.
French Interior Minister Manuel Valls described the killings as "intolerable".
The motive for the shootings is unclear. Some 40,000 people have died in the 25-year conflict between the Turkish state and the PKK.
However, Turkey has recently begun talks with the jailed PKK leader Abdullah Ocalan, with the aim of persuading the group to disarm.
"The scene [of the crime] could give rise to the idea that this was an execution, but the investigation will have to establish the exact circumstances of this incident," a police source told French reporters.
One of the women, Fidan Dogan, 32, worked in the information centre of the Kurdish institute.
A Kurdish news website in France has identified a second as Sakine Cansiz, a founder of the PKK, while the third is said to be a representative of the Brussels-based National Congress of Kurdistan.