The incident came a day after Turkish media reported that jailed PKK leader Abdullah Ocalan had agreed the outlines of a deal with the authorities in Ankara that could lead to the rebel movement laying down its weapons in March. In return, the Kurds would receive guarantees their cultural identity would be protected and jailed Kurdish leaders set free. Such a deal would be highly controversial, both among hardline Turkish nationalists and sections of the PKK opposed to compromise.

Kurdish activists protesting in Paris after news of the killings broke blamed Turkish agents, while officials in Ankara suggested internal PKK divisions were a more likely explanation.

Didier Billion, an expert on Turkey and the Kurds at the Paris-based Institute for International and Strategic Relations, was sceptical about the possible involvement of Ankara.

"I can't see the interest of the Turkish state in eliminating these three activists," he said, suggesting internal PKK divisions were a more likely motive. "We know that there is a radical faction within the PKK that is opposed to any dialogue. You can't rule out the theory of this being the work of people opposed to a deal between Ocalan and Turkey."

The PKK raises funds through a "revolutionary tax" on Kurdish expatriates that authorities in several countries have condemned as extortion. Several PKK leaders have also been designated by the United States as drug traffickers.

Dorothée Schmid, the French Institute for International Relations' director of Turkey studies, described Cansiz as "close to Ocalan, one of his mouthpieces". That may have made her a target for opponents of the nascent peace process, either from elements of the Turkish state or from PKK radicals, Schmid said.

"There is, in Turkey, a kind of state within the state, with a mix of ultranationalist activists, the secret services, the mafia and the army," she said. "We have seen an increase in nationalism … There are lots of people opposed to an accord with the PKK.

"For the moment, we don't know what is in it, but there is talk of Ocalan being freed, which many Turks will find hard to swallow."

Schmid said the killings could exacerbate tensions within the PKK over the accord being negotiated by Ocalan. "If these assassinations give credence to the idea that the deal being discussed is in Turkey's favour, there could be a split in the leadership."

A spokesman for Turkey's ruling Justice and Development Party, Huseyin Celik, said the nature of the killings pointed to a PKK feud. "We know the PKK terrorist organisation has carried out thousands of inside executions for years now," he said. "This is something inherent to terrorist organisations."

The Kurdish question has taken on particular urgency with the rise of Kurdish groups in northern Iraq, where they control an autonomous zone, and in Syria. Ankara fears that Syrian President Bashar al-Assad could encourage Kurds to feed militancy in Turkey.

Female militants have played a significant role in the PKK's insurgency. In some cases, desire to avenge the killing of other family members was the motivation for joining, for others it was a way out of family repression, analysts say.