SAN FRANCISCO: Thousands of people took to the streets in US cities on Friday to denounce the fatal police shootings of two black men, marching the day after a gunman killed five police officers watching over a similar demonstration in Dallas.
Protesters clogged roadways in New York City, Atlanta and Philadelphia, and events in San Francisco and Phoenix also drew large crowds. Media did not report any immediate instances of major clashes or injuries.
Fox10 News reported at noon on Saturday Bangkok time that police deployed tear gas or pepper spray in attempt to disperse advancing crowd in Phoenix.
Thousands marched in Atlanta in what appeared to be the largest demonstration, chanting and waving signs demanding justice, video posted to social media showed. Footage from broadcasters showed the massive crowd facing off with dozens of police vehicles that were stopped on a local interstate highway.
Atlanta mayor Kasim Reed tweeted that the rally was largely peaceful, though about 10 people had been arrested.
Friday was the second day of demonstrations against use of force by police in the wake of the fatal shootings of 32-year-old Philando Castile near St. Paul, Minnesota and 37-year-old Alton Sterling in Baton Rouge, Louisiana.
Castile was killed by police during a traffic stop on Wednesday, and his girlfriend posted live video on the internet of the bloody scene minutes afterward.
Sterling was killed on Tuesday during an altercation with two white police officers outside a convenience store. Graphic video of that incident caused an outcry on social media.
"No justice, no peace, no racist police," demonstrators shouted late on Friday in Baton Rouge, where state and local police in riot gear tried to keep them from blocking a busy roadway.
'Black Lives Matter'
The two shootings stoked racial tension that has flared repeatedly across the country following the 2014 killing of Michael Brown, an unarmed black teen, by a white police officer in Ferguson, Missouri.
Thursday's demonstrations were largely peaceful until gunfire erupted at a Dallas rally that was winding down.
Authorities said 25-year-old Micah Johnson, a black US military veteran of the Afghan war who said he wanted to "kill white people", launched a sniper attack that killed five police officers and wounded nine other people.
President Barack Obama said he will cut short a foreign trip and visit Dallas next week as the shooting rampage in Dallas triggered urgent calls to mend troubled race relations in the United States.
Police found bomb-making materials and a weapons cache at Johnson, a Dallas area resident.
Five officers were killed in the late Thursday shooting, including a Dallas transit cop, while seven other officers and two civilians were wounded.
While the White House ruled out any link between the gunman and known "terrorist organisations," Johnson's Facebook page ties him to several radical black movements listed as hate groups.
Described to police as a "loner" with no prior criminal record, Johnson told negotiators before he died that he wanted to kill white cops in retaliation for the recent fatal police shootings of two black men.
The US Army said that Johnson served as a reservist for six years, including a tour of duty in Afghanistan.
The rampage revives an emotional debate over lethal use of force by police, and problems of alleged police bias toward racial minorities, especially African-Americans.
Leaders of the Black Lives Matter protest movement condemned the Dallas violence, but vowed to uphold planned weekend marches.
Addressing thousands of people at a prayer service in honour of the fallen officers, Dallas mayor Mike Rawlings urged Americans to "step up" to heal the country's racial wounds.
"We will not shy away from the very real fact that we as a city, as a state, as a nation are struggling with racial issues," he told the crowd.
Mr Rawlings echoed Mr Obama's message that black lives matter -- and so do "blue" lives, those of police officers.
"We must step up our game and approach complicated issues in a different way," Mr Rawlings said. "And race is complicated."
Mr Obama, who ordered flags on government buildings lowered to half-mast for five days, said that there was "no possible justification" for violence against police.
The president commented on the attacks from the Polish capital, where he was attending a Nato summit. He condemned the shootings as "vicious, calculated and despicable".
The White House said Mr Obama would return to the United States late on Sunday, one day ahead of schedule, and visit Dallas early next week.
The shootings -- which left nine wounded, seven of them police officers -- sparked chaos as people ran for their lives during a march by several hundred demonstrators in the city of 1.2 million, near the site where president John F Kennedy was assassinated in 1963.
The peaceful Dallas protest was one of several nationwide that prompted Obama to make an emotional appeal for urgent police reform.
The ambush marks the single biggest loss of life for law enforcement in the United States since the Sept 11, 2001 terror attacks.
"This must stop -- this divisiveness between our police and our citizens," Dallas police chief David Brown said.
Johnson was killed in a tense showdown with police in a parking garage, by a bomb robot sent in by officers after hours of negotiations and an exchange of fire.
"This was a well-planned, well-thought out, evil strategy," said Mr Brown of the gunman.
Bomb-making materials, weapons and ammunition were found in Johnson's home.
"He said he was upset about the recent police shootings," Mr Brown said. "The suspect said he was upset at white people. The suspect stated he wanted to kill white people, especially white officers."
Earlier, officials said three other people had been detained, but it was unclear if any remained in custody.
US Homeland Security Secretary Jeh Johnson said the gunman appeared to have acted alone.
However Texas governor Greg Abbott said police would "continue down every rabbit trail... ensuring that we eliminate any other possible suspects or co-conspirators who may have aided this gunman in any way."
The gunman told police he was not affiliated with any organised groups.
But Johnson's Facebook page ties him to a number of organisations listed as hate groups by the Southern Poverty Law Center, which studies such movements in the United States.
Groups that he "liked" include the New Black Panther Party (NBPP) and the Nation of Islam, both known for expressing virulently anti-Semitic and anti-white views, the SPLC said in a statement.
On his Facebook page, Johnson appears with his fist raised wearing an African style tunic against the backdrop of the red, black and green Pan-African flag, all reminiscent of the US black power movement of the 1960s.
Another of his "likes" is a group called the African American Defense League, whose leader called this week for bloody retaliation after the fatal shooting in Louisiana.
"We must 'Rally The Troops!'" the post read. "It is time to visit Louisiana and hold a barbeque. The highlight of our occasion will be to sprinkle Pigs Blood!"