A spokesman for the Italian rail company, Maurizio Furia, told The Associated Press in Rome that the train carrying migrants and political activists who support them wasn't being allowed to pass into Menton, France, from the Italian border station of Ventimiglia.
Italy recently started giving out temporary residence permits to some of the thousands of Tunisians escaping unrest in northern Africa in recent weeks. The Italians say the permits should allow the Tunisians to go to France under an accord allowing visa-free travel among many European countries.
French authorities say they will allow in only Tunisians with the financial resources to live in France independently.
Italy insisted that the temporary permits were valid for entry into other European nations adhering to the visa-free Schengen travel accords.
"We have given the migrants travel documents, and we gave everything (else) that is needed, and the European Commission recognized that, it has said that Italy is following the Schengen rules," Italian Interior Minister Roberto Maroni said in an interview on Italy's Sky TG24 TV.
Visa "free travel is legitimate for all those with the papers and who want to go to France," Maroni said.
Maroni is a top officials of the anti-immigrant Northern League party, a main coalition partner of Premier Silvio Berlusconi.