|Photograph: Joe Penney/Reuters|
Three cops were killed and three others injured.
This follows the recent killing of a black man by police in the city, which sparked protests. That, and another police killing police in Minnesota, triggered a revenge attack by a black army veteran who shot dead five officers in the city of Dallas.
Mobile phone footage from the scene showed police cars arriving at a road intersection. Several shots were then heard.
Baton Rouge's local sheriff's department spokeswoman told WAFB TV the incident began shortly before 09:00 local time and was being treated as "an active situation", with road closures in the area.
A witness interviewed by the station said the shooting appeared to have broken out before law enforcement officers arrived at the scene.
Another witness said she saw a gunman wearing a black mask and military-style clothing.
One suspect is dead and two others may still be at large.