The bodies of Sakine Cansız, a founder of the Kurdistan Workers Party (PKK) in the early 1980s, and her two fellow activists were found in the early hours of Thursday (10 January) at an institute in the French capital that has close links to the PKK.
They appeared to have been shot in the head, a French police source said. Kurdish media said one woman was also shot in the abdomen. Workers had broken in to the room at the Information Centre of Kurdistan after seeing blood stains on a door.
Cansız was a prominent PKK figure, initially as a fighter and later in charge of the group's civil affairs in Europe, according to a Kurdish lawyer who knew her. A 1995 photograph shows her standing next to militant leader Abdullah Öcalan, wearing olive battle fatigues and clutching an assault rifle.
Öcalan is now in a Turkish jail and the killings came shortly after Turkey announced it had resumed peace negotiations with him - something likely to anger hardliners within the PKK (see background).
The Turkish government and PKK have agreed a framework for a peace plan, according to Turkish media reports, in talks which would have been unthinkable in Turkey only a few years ago. Öcalan is widely reviled by Turks who hold him responsible for a conflict that burns at the heart of the nation.
French investigators gave no immediate indication of who might be behind the murders. The PKK has seen intermittent internal feuding during an armed campaign in the mountainous Turkish southeast that has killed some 40,000 people since 1984.
Turkish nationalist militants have in the past also been accused of killing Kurdish activists, who want regional autonomy. But such incidents have been confined to Turkey.
"The choice of Cansız as a target is because she was symbolic of the Kurdish movement," said Franck Cecen, a Kurdish lawyer in Paris who met Cansız at least half a dozen times and described her as exceptionally well-spoken and well-educated.
"She had been one of its founding members, she had spent years in prison for her convictions, and she had become a historical figure," he told Reuters, adding that he found it hard to believe fellow Kurds would have taken her life.
"It is difficult to imagine that this was done by a Kurdish cell," he said. "Everyone is talking about a Turkish role."
Erdoğan: 'This may be an internal reckoning'
Turkish Prime Minister Recep Tayyip Erdoğan said it was too early to apportion blame: "This may be an internal reckoning," he said. "We are engaged in a struggle against terrorism. We want to make progress, but there are people who don't want this. This could be a provocative undertaking by these people."
The killings came shortly after Erdoğan's government announced it had resumed talks with Öcalan, who has been confined on a prison island near Istanbul since 1999. Talks to end the conflict would almost certainly raise tensions within the Kurdish movement over demands and terms of any ceasefire.
Among a crowd that gathered behind police lines at the Paris Kurdish institute were onlookers chanting slogans and waving yellow flags bearing Öcalan's likeness. France is home tens of thousands of Kurdish immigrants, of who some are PKK activists.
"Rest assured that French authorities are determined to get to the bottom of these unbearable acts," French Interior Minister Manuel Valls said at the scene, adding the killings were "surely an execution". His predecessor, Claude Guéant, said Turkey's engagement in the peace process led him to conclude it was unlikely that Ankara's agents were behind the killings.
Any Turkish government contacts with the PKK, deemed a terrorist group by Ankara, Washington and the European Union, are highly controversial in the Turkish political establishment.
Valls identified one of the victims as the head of the Information Centre and said homicide and anti-terrorism units had been assigned to investigate the murders. A police source confirmed that all held Turkish citizenship.
The two victims other than Cansız were named as Fidan Dogan, 28, and Leyla Soylemez, 25.