A judicial source said on Monday that police searched several premises and that the suspects were taken to the headquarters of the domestic intelligence agency DST for questioning.
They can be held for four days, then must be placed under formal investigation by a judge or released.
Police believe the suspects are linked to Algeria's Salafist Group for Prayer and Combat (GSPC).
The head of the French national police said in July the group had contacted al-Qaida's leader in Iraq, Abu Musab al-Zarqawi, about carrying out attacks in France.
Judicial officials said that among those detained on Monday was a 35-year-old Algerian recently freed after a 10-year jail term for his role in the 1995 attacks in France by Algeria's Armed Islamic Group, which killed 10 people.
France fears attacks in spite of its outspoken opposition to the US-led war in Iraq.
Paris shares intelligence with the United States and Britain, Washington's main military ally in Iraq.
The dawn raids in the Yvelines and Eure regions outside Paris were carried out as Interior Minister Nicolas Sarkozy was about to unveil tough anti-terrorism laws, France's response to bomb attacks in London on 7 July.
New measures include increased use of closed circuit television surveillance and a law to force internet cafes and mobile phone operators to keep records.
The mobile phone and internet measures will be covered by a three-year time limit, the newspaper Le Figaro reported, and will need parliamentary approval to stay in force after 2008.
Separately, the Justice Ministry wants to impose tougher prison sentences for those convicted of playing secondary roles in terrorist plots.
It is also considering extending the period suspects can be questioned by police to six days from four.