A train carrying Tunisian immigrants from Italy has been halted at the French border in an escalation of an international dispute over the fate of North African migrants fleeing political unrest for refuge in Europe.
A spokesman for the Italian rail company, Maurizio Furia, said the train carrying migrants and political activists who support them was not being allowed to pass into Menton, France, from the border station of Ventimiglia.
Italy lodged a protest with the French government, calling the move "illegitimate and in clear violation of general European principles" the Italian Foreign Ministry said.
Foreign Minister Franco Frattini ordered his envoy in Paris "to express the strong protest of the Italian government".
Italy has been giving temporary residence permits to many of the roughly 26,000 Tunisians who have gone to Italy to escape unrest in northern Africa in recent weeks. Many of the Tunisians have family ties or friends in France, and the Italian government says the permits should allow the Tunisians to go there under accords allowing visa-free travel among many European countries.
France says it will honour the permits only if the migrants prove they can financially support themselves and it has instituted patrols on the Italian border - unprecedented since the introduction of the Schengen travel-free zone.
Germany has said it would do the same.
European nations have been increasingly and bitterly sparring over the issue.
"We have given the migrants travel documents, and we gave everything (else) that is needed, and the European Commission recognised 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," said Mr Maroni, a top official of the anti-immigrant Northern League party, a main coalition partner of Premier Silvio Berlusconi.