BATON ROUGE, LOUISIANA (REUTERS, AFP) - Three police officers were shot to death and three others wounded in Baton Rouge, Louisiana on Sunday (July 17), said police, as the country remained on edge in the wake of police shootings of black men and the killings of five Dallas officers.

The officers in Baton Rouge were responding to a call of a man with a gun when shots were fired. Two Baton Rouge police officers and one sheriff's deputy were killed.

Officials said that the gunman was shot dead and that there were no other suspects at large. The motive for the shooting was not immediately clear.

"We believe the person that shot and killed our officers, that he is a person that was shot and killed at the scene," Louisiana State Police Superintendent Colonel Mike Edmonson told reporters.

"What we do not believe is we have any other shooter held up in the Baton Rouge area."

One of the wounded officers "is in critical condition fighting for his life as we speak, (a) 41-year-old", 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 (9.40pm Singapore time), 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 identified the suspect as Gavin Long, a 29-year-old African-American from Kansas City, Missouri. Investigators suspect a 911 emergency call may have been used to lure police to the scene, the official said on condition of anonymity.

Witness Brady Vancel told CBS television affiliate WAFB that he saw what may have been gang members shooting at each other before police arrived.

"This has nothing to do with any situation," he said, referring to controversies surrounding a series of high-profile shootings involving police.

He said 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.

Earlier, police said they were looking for the two suspected surviving shooters, and were checking the shooting scene with a robot to make sure there were no explosives, said police spokesman L'Jean McNeely.

WAFB aired video footage of police responding to the scene in Baton Rouge. Multiple shots could be heard as civilian cars quickly backed away.

While the scene of the shootings was contained, police warned residents to stay away from the area, near Airline Highway, which is a mile from the Baton Rouge Police Department headquarters, where dozens of protesters were arrested earlier this month.

President Barack Obama, in a statement on Sunday, condemned the shooting as "cowardly".

"For the second time in two weeks, police officers who put their lives on the line for ours every day were doing their job when they were killed in a cowardly and reprehensible assault," Obama said.

"These are attacks on public servants, on the rule of law and on civilised society, and they have to stop."

"We may not yet know the motives for this attack, but I want to be clear: there is no justification for violence against law enforcement. None. These attacks are the work of cowards who speak for no one. They right no wrongs. They advance no causes," said Obama.

"There is no place in the United States for such appalling violence," his Attorney General Loretta Lynch said.

Donald Trump, the presumptive Republican presidential nominee, took to Twitter to say: "We are TRYING to fight ISIS, and now our own people are killing our police. Our country is divided and out of control. The world is watching."

Democractic rival Hillary Clinton also urged Americans to "stand together to reject violence and strengthen our communities".

"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." He vowed that "every resource is going to be available to be used to bring these perpetrators, if there's more than one, to justice," pointing to support at the federal, state and local levels.

It was not immediately clear whether there is a link between Sunday's shootings and the recent unrest over police killings of black men in Baton Rouge and Minnesota that were captured in shocking video footage that went viral online.

A wave of protests against police violence in Baton Rouge and other cities erupted after Alton Sterling, a 37-year-old African-American father of five, was shot and killed at close quarters by law enforcement officers on July 5.

At a rally in Dallas to protest Sterling's killing and the incident in Minnesota, a gunman opened fire on white officers, killing five of them.

The Black Lives Matter civil rights movement has called for police to end racial profiling, bringing the issue to national attention ahead of the US presidential election on Nov 8.

The Justice Department, which has opened a federal probe into Sterling's death, declined to comment on Sunday's shootings.

A White House official added that the White House has also been in contact with local officials and has offered assistance.