Paris, July 18

A special kind of iron curtain came down across central Paris today, with the beginning of an Olympics anti-terrorism perimeter along the banks of the River Seine sealing off a kilometres-long area to Parisians and tourists who hadn't applied in advance for a pass. The words on many lips were "QR code," the pass that grants access beyond snaking metal barriers that delineate the security zone set up to protect the Olympic Games' opening ceremony on July 26.

"I didn't know it started today," said Emmanuelle Witt, a 35-year-old communications freelancer who was stopped by police near the Alma bridge while biking across town. She desperately went on her phone to fill out the online form to get her QR code, unaware that the vetting process could take several days.

Those with the precious code — either on their phones or printed out on pieces of paper — passed smoothly past police checkpoints at gaps in the barriers taller than most people. —AP