Spain's temporary suspension of passport-free entry from most of Europe kicked in from midnight on Friday.
It's dropping the Schengen accord for a week while a summit of the European Central Bank takes place in Barcelona.
Spanish authorities say the tighter border controls are needed to stop foreign nationals joining what could be violent street protests.
Extra police have been drafted in to carry out border checks.
A total of 6, 500 officers are due to be deployed in Barcelona during next week's summit.
Windows were pelted with rocks and rubbish bins set alight in the city during last month's nationwide general strike over unemployment and spending cuts.
The government fears the ECB meeting could re-ignite further chaos.
Paul Chapman, Reuters
