The French interior minister has joined Muslim leaders at the main mosque in Paris to pray for the release of two French journalists abducted in Iraq.
The journalists say they fear for their lives
Worshippers applauded as Dominique de Villepin spoke of the unity of French Muslims and non-Muslims.
French Muslim leader Dalil Boubakeur described the men as "our countrymen" and urged the kidnappers to free them.
The kidnappers have demanded that France repeal a ban on Islamic headscarves in French state schools.
The law introducing the ban is due to come into effect on Thursday. The government has refused to withdraw it.
The BBC's Angus Roxburgh, in Paris, describes Mr de Villepin's visit to the mosque as highly symbolic.
Ban proposed in December 2003 and backed by parliament in March
Due to come into effect at start of new school year on Thursday
Lays down that "conspicuous" religious items may not be worn in schools
Forbidden items will include Muslim headscarf, Jewish skullcap and large Christian crucifixes
He says French Muslims attended to demonstrate their solidarity and their Frenchness - and to distance themselves from the Iraqi kidnappers.
Meanwhile, an influential Sunni Muslim organisation in Iraq, the Committee of Ulema, said it had failed to make contact with the kidnappers and feared the journalists might be killed.
A group calling itself The Islamic Army in Iraq says it is holding the two men - Christian Chesnot of Radio France Internationale and Georges Malbrunot of Paris daily newspaper Le Figaro.
Arab TV station al-Jazeera showed a video on Monday in which both men, speaking in English, called for the law banning headscarves to be overturned - and for French people to demonstrate for its repeal.
"We might die at any moment if this law is not repealed," Mr Malbrunot said.
The Arab League has said its contacts in Iraq believe the kidnappers have extended their deadline for the headscarf law's repeal until Wednesday evening, and not Tuesday as previously reported. The original deadline was Monday evening.
French Foreign Minister Michel Barnier has held meetings in Jordan and Egypt during a visit to the Middle East to seek support for attempts to get the men released.
Jordan has said it will use its contacts in Iraq - developed in freeing its own kidnapped citizens - to try to resolve the crisis. At least nine Jordanian hostages have been freed in Iraq in the last two weeks.
Arab leaders across the region - including Palestinian leader Yasser Arafat and Libyan leader Muammar Gaddafi - have urged that the two men be freed, describing France, which strongly opposed the US-led invasion of Iraq, as a friend of Arabs.
The law banning headscarves in schools is a central policy, designed to maintain France's tradition of strictly separating state and religion.
It forbids state school students from wearing "conspicuous" religious apparel. Jewish skullcaps and large Christian crosses are also banned.
Dozens of foreigners have been abducted by militants in Iraq in recent months.
Most groups have employed kidnapping with the aim of driving out companies, individuals and troops helping US forces and the new Iraqi government.