French, Italian and Tunisian protesters had planned to board what they called a “train of dignity” in Ventimiglia and travel to Nice in southern France, in defiance of the limits on immigration introduced in the wake of recent upheaval in North Africa.
The demonstrators want to “open borders, guarantee free access to European territory, and remind people that no human being is ‘illegal’”, according to organisers.
But all mainline train services from Italy to France were cancelled on Sunday afternoon.
Activists said they would sleep at the station and attempt to board a train on Monday.
Rome has asked for clarification on France’s decision to block the services, which “appear to be illegal and in clear violation of European principles”, according to Foreign Minister Franco Frattini.