MADRID — Spain's government warned it would implement passport and nationality checks on Italian travelers starting at midnight local time if Rome did not comply. The measure is a direct response to Italy's border restrictions on Spanish citizens, which Madrid said violates the Schengen Agreement's free movement principles.

Spanish authorities gave Italy a deadline of Sunday, Aug. 9, to lift its temporary controls. Madrid said it would take "proportionate measures" if Rome did not comply, effectively mirroring Italy's actions.

Italian border authorities activated temporary document screening for selected passengers arriving from Spain on Aug. 1. Those checks followed a large-scale migration incident in Spain's North African enclave of Ceuta, which Rome cited as a security concern.

Italy's initial inspections involved officers requesting identity documents from both European Union and non-EU passengers, primarily on selected maritime and air routes originating from Spain.

The Schengen Agreement generally allows for border-free travel among member states. Spain's government maintains that Italy's reintroduction of checks breaches the agreement.

While EU, EEA and Swiss citizens retain free movement rights, they are advised to carry a valid passport or national identity card. The reinstated checks are temporary and do not alter the validity of existing Schengen visas or residence permits for non-EU passport holders already within the Schengen area.

Passengers traveling from Spain to Italy had already reported identity document requests at Rome Fiumicino Airport on Aug. 1. Spain's new controls could cause similar delays for those traveling in the opposite direction.

The dispute reflects broader tension within the European Union over migration and internal border management, as member states debate the balance between national security and the principles of the Schengen zone.