WASHINGTON – A black gunman shot dead three police officers in the Louisiana capital of Baton Rouge on Sunday, in the latest spate of violence involving law enforcement.

The shooting, which also wounded three other officers, took place in a city scarred by high racial tensions and numerous protests against police brutality since the death July 5 of Alton Sterling, a black man shot at point-blank range by police.

Two days after the Sterling shooting, a gunman ambushed police officers, killing five, during a demonstration triggered by Sterling’s death at the hands of police and that of another African-American man in Minnesota whose dying moments were captured in shocking video footage that went viral online.

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

One of the wounded officers "is in critical condition fighting for his life as we speak," Edmonson said. The other two officers were in stable condition.

"With God’s help, we will get through this. To me, this is not so much about gun control as it is about what’s in men’s hearts," said Edmonson, who like some of his colleagues who spoke in the press conference, was clearly shaken.

"And until we come together as a nation, as a people, to heal as a people, if we don’t do that and this madness continues, we will surely perish as a people."

The shooting took place along a highway around 8:40am (1340 GMT), after police responded to a call about a man carrying a rifle.

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

Some reports said the suspect was wearing a mask. US media citing unnamed sources identified the suspect as Gavin Long, a 29-year-old African American from Kansas City, Missouri whose birthday was on Sunday.

A recent series of high-profile shootings involving police have exposed deep fault lines through US society, reviving long-running debates about racial prejudice and an epidemic of gun violence.

’Cowardly’

President Barack Obama, who has had to address multiple mass shooting tragedies during his term, condemned the Baton Rouge shooting as "cowardly" and demanded an end to such violence.

"It is so important that everyone... right now focus on words and actions that can unite this country rather than divide it further," Obama said.

"We don’t need inflammatory rhetoric. We don’t need careless accusations thrown around to score political points or to advance an agenda. We need to temper our words and open our hearts, all of us."

The first African American president of the United States, Obama has made repeated calls for racial unity.

"Regardless of motive, the death of these three brave officers underscores the danger that police across the country confront every single day, and we as a nation have to be loud and clear that nothing justifies violence against law enforcement," Obama told reporters at the White House.

"This has happened far too often."

Obama pledged the federal government’s full support in the investigation of the incident.

Donald Trump, the presumptive Republican presidential nominee, expressed grief in a Facebook post.

"How many law enforcement and people have to die because of a lack of leadership in our country? We demand law and order," he wrote.

Witness Brady Vancel told CBS television affiliate WAFB he saw two men running away and a third lying motionless on the ground. At least one was carrying what appeared to be an AR-15 automatic rifle amid the sound of gunfire.

The races of those possible shooters and the police officers involved were not immediately clear.

Multiple shots could be heard as civilian cars quickly backed away during the incident.

’Unspeakable, heinous attack’

"Today has been a very tough day here in Baton Rouge and in Louisiana and in our country – an absolutely unspeakable, heinous attack on law enforcement here in Baton Rouge," Louisiana Governor John Bel Edwards said.

"The violence, the hatred, just has to stop."

Last week, police arrested more than 100 protesters taking part in a demonstration against police brutality in Baton Rouge under the banner of the Black Lives Matter movement.

Sterling’s aunt Veda Washington-Abusaleh made a tearful plea for an end to the violence.

"We don’t want no more bloodshed. Leave. Go home. Go wherever you come from. This is our house. You can’t come in our house killing us," she said in an emotional interview with local television.

"No justice! No peace! That’s what we’re calling for. Stop this killing!"

Sunday’s shooting also plays into a debate about gun control in a country in which firearms killed some 13,440 people last year, according to the Gun Violence Archive.

Last month, Democratic lawmakers, pushing for tougher gun-control laws after a massacre in a Florida gay nightclub killed 49 people, staged a virtually unprecedented 24-hour sit-in in Congress after Republicans refused to allow a vote on two widely supported measures. — AFP