The Louvre museum in Paris was evacuating all visitors and staff and closing early on Saturday after it received a written threat.
It said the move was linked to the government’s decision to put France on high alert after a fatal school stabbing by a suspected extremist.
The Louvre communication service said no one has been hurt and no incident has been reported.
Paris police said verifications in the museum are under way.
The former royal palace at Versailles also received bomb threats, a national police spokesperson said. The palace and its sprawling gardens are being evacuated while police examine the area, the spokesperson said.
Alarms rang out through the vast museum in central Paris overlooking the Seine River when the evacuation was announced, and in the underground shopping centre beneath its signature pyramid.
Police cordoned off the monument from all sides, and the underground access, as tourists and other visitors streamed out.
Videos posted online showed people leaving, some hurriedly and some stopping to take photos, others apparently confused about what was happening.
The French government raised the threat alert level and is deploying 7,000 troops to increase security after Friday’s school attack.
The government is also concerned about fallout in France from the war between Israel and Hamas.
The Louvre, home to masterpieces such as the Mona Lisa, welcomes between 30,000 and 40,000 visitors per day.
