The people arrested in the cities of Bordeaux and Toulouse are suspected of being senior figures within the regional structure of the organisation, the sources said.
The arrests came as German federal prosecutors on Tuesday pressed charges against a 46-year-old Turkish man suspected of raising money for the PKK throughout Europe.
The PKK, which took up arms in its campaign for autonomy in southeast Turkey in 1984, is branded a terrorist group by Ankara and its Western allies.
More than 40,000 people, mostly Kurds, have died in the conflict.
Three Kurdish women activists were shot dead in Paris last month. The driver of one of the women has been charged with their murder.
The killings came against a background of tentative peace talks between Turkey and jailed PKK leader Abdullah Ocalan.