UPDATE 5.05PM and 5:43PM: A FIFTH officer has died after the sniper attack on police in Dallas.
Other officers were still in negotiation with a suspect who had been exchanging gunfire with police at a parking garage well into the morning.
Local media reported the suspect later shot himself.
A woman who was marching with the protest was also shot while she attempted to shield her sons during the shooting, AP reported.
Mark Hughes, the man police earlier falsely identified as a suspect, has also spoken to media.
He said he was unaware his picture had been sent around the world as a person of interest.
Video also emerged of Mr Hughes earlier handing his gun, which he was legally allowed to openly carry, to a police officer.
In other cities across America, protests against the police killing of Philando Castile and Alton Sterling went ahead.
Police in Minnesota, where Philando Castile was shot dead during a traffic stop, fired rubber bullets at protesters.
Mr Castile was shot after telling officers he had a gun in the vehicle. He was legally permitted to carry the weapon.
Protesters spent the night gathered in major spots in the city, including in a large crowd outside the governor's residence.
UPDATE 3:39PM: DALLAS Mayor Mike Rawlings and the Dallas Police Chief David Brown have briefed the country on the aftermath of a shooting that has left four police officers dead and eight others wounded.
Mr Rawlings said the downtown area of Dallas would remain a crime scene into the next day and called on members of the public to stay away from the area.
"It is a heartbreaking morning, to lose these four officers that proudly served our citizens," he said.
Officer Brown said it had yet to be determined whether the snipers were connected to the protest. Three people in total were in custody.
He said they were negotiating with a suspect who had been exchanging gunfire with officers and who told officers 'the end was coming'.
Officer Brown said the suspect also threatened to kill more officers.
He said they were not yet comfortable all suspects were in custody.
Officers had also earlier stopped two suspects who had sped away with suspicious bags in their car.
Mr Brown said the police department would pursue any connection between the heated comments on social media that made threats towards police officers and the shootings.
He said officers were waiting for the suspects to "break" and offer some clue to their motive.
UPDATE 2.36PM: DALLAS police have officially announced that a fourth officer has died.
In a statement, the department said the person of interest whose picture was released had turned himself in.
A second suspect was in a shoot-out with officers and is now in custody.
Dallas PD said a suspicious package had also been found and was being assessed by the Dallas bomb squad.
UPDATE 2.25PM: MEMBERS of the public have defended a man Dallas police have labelled a suspect in the sniper shooting that has killed four police officers.
The man's brother told U.S media the suspect, a man named Mark Hughes who police tweeted a photo of, had been mistaken for the real sniper.
He was wearing a similar shirt as the suspect and carrying a weapon but social media users highlighted video footage of the first shots being fired and say the man can be seen on the ground with other protesters.
The snipers fired from a building.
Man tells CBS Dallas person of interest in photo is brother Mark Hughes; handed weapon to cops when shooting broke out; isn't the shooter— Dennis Romero (@dennisjromero) July 8, 2016
UPDATE 2.09PM: Reports suggest at least four officers are dead out of 11 who were shot when two snipers attacked police during a Black Lives Matters protest in Dallas.
The Dallas Police Department tweeted a photo of one of the suspects as it updated the world on the number of victims.
There were about 100 police officers onsite to protect protesters.
"At 8.58, our worst nightmare happened," Dallas Mayor Mike Rawlings said.
He told media the suspect had also threatened to plant a bomb in downtown Dallas.
The shooting played out on social media as members of the public were recording the protest.
The protest was instigated by the police shootings of two African American men in the past week.
This is one of our suspects. Please help us find him! pic.twitter.com/Na5T8ZxSz6— Dallas Police Depart (@DallasPD) July 8, 2016
UPDATE: THREE officers are dead and several others are in critical condition after two snipers shot at police during a protest against the police shootings of two African American men.
Dallas Police Chief David Brown said three officers were killed and another three were in critical condition.
He said two snipers were responsible for the shooting and remained at large.
"Tonight it appears that two snipers shot ten police officers from elevated positions during the protest/rally," Dallas police Chief David Brown told NBC News in a statement.
"Three officers are deceased, two are in surgery and three are in critical condition. An intensive search for suspects is currently underway.
"Please keep us in your thoughts and prayers tonight."
Video footage shows officers taking cover behind cars as shots rang out in the street.
The Dallas Police Department tweeted a photo of one of the suspects.
There were also reports of a shooting at a downtown hotel, though it remains unclear if the incidents were related.
Details remain scarce but the report comes at a time of clear racial tension in the United States after two African American men were shot and killed by police in recent days.
Witnesses captured video of Aton Sterling's death in Baton Rouge, Louisiana, on their mobile phones.
Philando Castile's girlfriend streamed footage of him bleeding to death beside in the car seat beside her on Facebook Live.
EARLIER: PROTESTS have erupted across the United States after police fatally shot Minnesota school worker Philando Castile during a traffic stop.
The aftermath of Mr Castile's shooting was live streamed on Facebook as his fiancé, Diamond Lavish Reynolds, chose to record what happened to hold police officers to account.
His death is the second high-profile shooting of an African American man by police in the US in the past week.
Mr Castile, a 32-year-old who worked in the cafeteria of a local school, was stopped on Wednesday.
In the video she filmed after officers shot him, Ms Reynolds explains how officers shot Mr Castile four times after he told them he had a gun in the car.
She said he had a permit to carry the pistol. The video shows a police officer pointing a gun into the car as Mr Castile lays injured in the driver's seat.
Ms Reynold's four-year-old daughter was in the back seat when Mr Castile was shot.
In the video that has been watched more than four million times, she said Mr Castile immediately stopped reaching for the glove box once the officer told him not to move.
"You shot four bullets into him sir," she said. "He was just reaching for his licence."
The live streaming shows officers ordering Ms Reynolds out of the car and a police officer can be heard handcuffing her.
"You're just being detained until we can sort this out," he says
In the days since his death, thousands of people have gathered to protest against the continued police shootings of African American people.
New York's 5th Avenue was blocked by a large crowd marching against both his death and the shooting earlier this week of Alton Sterling.
Ms Reynolds spoke publicly after she was released from police custody and said she live streamed the aftermath of the shooting to show the world the police were not there to protect and serve.
"They did this to my daughter and they did this to me, and I want justice and I want peace," she said.
Governor of Minnesota Mark Dayton requested the Department of Justice begin an immediate federal investigation into the shooting.
"A terrible tragedy has befallen the people of Minnesota."
"Nobody should be shot and killed while they're still in their car."
"I'm heartbroken for Minnesota."
"Would this have happened if the driver or passenger were white? I don't think so."
President Barack Obama also made a statement calling out the rate African American people are shot by police.
"Now let me just say that we have extraordinary appreciation and respect for the vast majority of police officers who put their line on the lives every day. They have a dangerous job. It is a tough job. And as I've said before, they have a right to go home to their families, just like anybody else on the job," he said.
"And there are gonna be circumstances where they're gonna have to make split second decisions. We understand that.
"But when we see data that indicates disparities in how African Americans and Latinos may be treated in various jurisdictions around the country, then it's incumbent on all of us to say we are better than this. We are better than this."
A federal investigation has also been launched into Mr Sterling's death.
He was shot by officers in Baton Rouge.