"The US embassy in Paris informs US citizens that there has been a police action on the Champs Elysees in Paris," the embassy stated. "US citizens are advised to avoid the area, heed instructions of local authorities and monitor local media for updates."
At least one police officer was injured after an assailant opened fire on a police vehicle near the Franklin Roosevelt subway stop in Paris around 9 p.m. (8 p.m. GMT) on Thursday.
A second officer and the assailant have been reported killed.
Police have placed the area on lockdown and are searching homes and a vehicle believed to belong to the shooter.
The Paris prosecutor’s office counter-terror unit opened an investigation into the incident.