Most were foreigners found to have irregularities in their identity papers, the official said, adding, 'There could be more such operations today and in days to come.' A rail terminal, the Gare de l'Est, and a nearby underground station were evacuated after a bomb threat was received, police said.
France on Saturday dismissed a demand by the military wing of the Islamic Salvation Front (FIS) to free the 17 Muslims who were seized following Wednesday's attack on a French embassy housing compound in Algiers in which seven French officials were killed.
The militant Algerian Armed Islamic Group (AIG), which claimed responsibility for the attack, on Saturday warned Algerian students and teachers to stay away from schools and universities and said any which stayed open would be blown up or burnt down.
The 17 detainees, accused by the Interior Minister, Charles Pasqua, of 'support for terrorism' while on French soil, are being held in an army camp in the village of Folembray, north-east of Paris.
Paris has strongly supported Algeria's army-backed authorities since they cancelled a general election in January 1992 which the FIS was poised to win. At least 4,000 Algerians and 56 foreigners have been killed in subsequent waves of violence. The FIS has been banned in Algeria and is a prime target of a French crackdown on suspected fundamentalists.
'The arrest and detention of these brothers, most of them members of the FIS or sympathisers in the cause for which they are fighting, means that France has declared war on the FIS and on Algerian Muslims,' the FIS military wing - called the Islamic Salvation Army (AIS) - said in a statement circulated in Algiers and obtained in Paris.
'France should renounce this policy of belligerence and free our brothers or it will assume responsibility for what will happen at the hands of the mujahedin affiliated with the AIS,' said the statement.
Interior Ministry officials said a tightening of security across France had been ordered in anticipation of such threats when the decision was made to round up suspected activists.