Three police officers have been shot dead in the US city of Baton Rouge and five others injured, US media reports say.
A police spokesman said the scene had been "contained". It was not clear if any suspects have been detained.
Reports say a lone gunman opened fire with an assault rifle.
It follows the recent killing of a black man by police in the city. That, and a police shooting in Minnesota, led to protests across the US.
The killings triggered a revenge attack by a black army veteran who shot dead five officers in the city of Dallas.
Baton Rouge police have warned residents to stay away from the scene of the latest shooting, which was near police headquarters and Airline Highway.
Footage shown on a local TV channel, filmed on a mobile phone, showed police cars arriving at a road intersection. Several shots were then heard.
Baton Rouge mayor Kip Holden said he had spoken to White House officials in Washington, who had offered assistance. He said it was "a defining moment" for community relations., BBC reported.