Baton Rouge

Officers were responding to a call of shots fired when they were shot in what Baton Rouge Mayor Kip Holden described as "an ambush-style deal."

Louisiana State Police Superintendent Colonel Mike Edmonson said the gunman behind the shootings was killed and there are no suspects at large. The motive was not immediately clear.

"Baton Rouge officers at a convenience store observed the individual. He was wearing all black standing behind a beauty supply store holding a rifle," Colonel Edmonson told reporters.

A suspect shot dead at the scene was thought to be the only gunman involved, police said. Reports earlier suggested there was more than one gunman.

President Barack Obama said nothing justified attacks on police officers.

It is not clear what the motive is, or whether there is any link to the killing by police of a black man in the city nearly two weeks ago.

The shooting of Alton Sterling and another killing of a black man in Minnesota, led to widespread protests across the US.

Key points:

• Two videos captured the moment when Alton Sterling, 37, was shot 5 times at close range by police
• Police confirm Mr Sterling was armed
• Federal authorities will handle the investigation, led by the Department of Justice civil rights division

Captured on at least two videos, the graphic images show Alton Sterling, 37, pinned to the ground and shot five times in the chest by two white police officers outside a convenience store.

The East Baton Rouge Parish Sheriff's Office said the men were found dead in a driveway after an argument broke out at about 12:30 a.m. Sheriff's office spokeswoman Casey Rayborn Hicks told the Advocate that the men were watching football and listening to music at a neighbor's house when they got into an argument over the music.

The suspected shooter was identified as Rodney Chemin, 60, and the three brothers as Joseph Allen, 57; Perry Allen, 55 and Mark Allen, 51. The four men were found dead outside Chemin's house.