With Parisians' nerves still on edge after Fridays shootings and suicide bombings, people suddenly all began running away from the square, a Reuters witness at the scene said.
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"There was crowd movement with apparently with no reason. We hadn't heard anything and all the people we questioned hadn't heard anything either," a police official at the square told Reuters.
TV pictures that had earlier been showing people gathered around a monument to commemorate those killed in Friday's militant shootings later showed the scene nearly empty.
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An official from the emergency services said some members of the public had believed they had heard gunfire.
There was also panicked movement of crowds outside a bar that had been the scene of a shooting on Friday, and where people had gathered in vigil Sunday evening. A second police official said that had also been a false alarm.
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