Former black Marine kills 3 policemen in ambush-style shooting

A black US Marine veteran killed three police officers in Baton Rouge before being shot dead, nearly two weeks after the fatal police shooting of a black man in the city that sparked country-wide protests and led to the massacre of five law enforcement officers.

The African-American gunman, identified by the media as 29-year-old Gavin Eugene long, dressed in black and armed with a rifle, shot the police officers in an "ambush-style" attack yesterday.

The motive of the shooting was not known but comes amid spiralling tensions across the city and the country between the black community and police amid the ambush on Dallas police officers where a sniper killed five officers.

Officials confirmed that three law enforcement officers died while three others were wounded during the shooting on Airline Highway in Baton Rouge, louisiana, over a kilometre away from police headquarters.

The gunman, a decorated former Marine sergeant who served in Iraq, was shot dead minutes later in the gunfight with police.

The shooter appeared to have attacked police officers on his birthday, police said.

Authorities initially believed that two other assailants might be at large, but hours later said that no other active shooters were in the city.

"The dead suspect in the Baton Rouge shooting was wearing all black and a mask," Baton Rouge Police Department Sgt Don Coppola said.

A witness told WBRZ-TV that a man, dressed in black with his face covered, was shooting indiscriminately when he walked out between a convenience store and car wash.

Police received a call of "suspicious person walking down Airline Highway with an assault rifle," a source said, adding that when police arrived, the man opened fire.

President Barack Obama condemned the shooting as "cowardly" assault and called for national unity, urging Americans and political leaders to avoid inflammatory words and focus on "uniting the country rather than dividing it".

"It is so important that everyone regardless of race or political party or profession, regardless of what organisations you are a part of, everyone right now focus on words and actions that can unite this country rather than divide it further," Obama said in an address to the nation from White House after the shooting.

"Attacks on police are an attack on all of us and the rule of law that makes society possible," he said.

"...I want to be clear: there is no justification for violence against law enforcement. None," Obama said.

According to reports, the gunman, served in the US Marines for five years starting in August 2005 as a data network specialist, and attained the rank of sergeant.

His Iraq tour lasted from June 2008 to January 2009.