These protests are sparked by fatal shooting of two black men, Alton Sterling and Philando Castile, by the police in Louisiana and Minnesota.
Thousands of protesters took to the streets in cities all across the US on Friday to mark their protest against the killings of two black men by police shootings this week.
The protests come one day after a gunman shot dead five police officers monitoring a similar demonstration in Dallas.
Protests in New York, Atlanta, Philadelphia, San Francisco and Phoenix, which witnessed large number of participants, were largely peaceful. However, according to local media and witnesses, police in riot gear used pepper sprays to disperse the crowds in Phoenix.
The protests were sparked by the fatal shooting of two black men – Alton Sterling, 37, and Philando Castile, 32 – by police in Louisiana and Minnesota.
Sterling, a father of five, was shot four to six times in the chest and back after an argument with police officers outside a Baton Rouge convenience store on Tuesday.
On Wednesday, another police shooting killed Philando Castile in Falcon Heights, Minnesota. The aftermath of his killing was captured by his fiancée in a live Facebook stream. The graphic video showing Castile in blood soaked white shirt was strongly decried on the social media.
"No justice, no peace, no racist police," demonstrators chanted late on Friday in Baton Rouge, where state and local police in riot gear tried to keep them from blocking a busy roadway.
A video clip on Twitter about today's protest in Detroit showed participants holding placards and chanting slogans as they marched on a street.
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 coming to a close.
Officials 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.
Police killed the gunman with a bomb-carrying robot after cornering him in a parking garage, ending an hours-long standoff.
Police ambushed in three other states
Police came under fire in three US states on Thursday and Friday, authorities said, possibly prompted by the same motivation behind the rampage in Dallas: police use of force against black people.
A man in Tennessee opened fire on a hotel and a highway, killing a woman, grazing a police officer with a bullet and wounding several others on Thursday because he may have been troubled by incidents involving black people and law enforcement, officials said.
Police officers also were ambushed and wounded in Missouri and Georgia on Friday, but officials did not know the motivation.
The National Rifle Association (NRA) faced criticism for failing to come out in defence of Philando Castile, who was shot and killed by a police officer after reportedly acknowledging that he carried a weapon with permit.
Two days after the killing of Sterling, the NRA posted a statement on Twitter, without mentioning his name.
Castile's family said that he had a concealed-carry permit for his weapon – a claim yet to be confirmed by the authorities. According to CNN, officials with the Minnesota Department of Public Safety and the Hennepin County Sheriff's Office said such data is private under state law.
Obama to visit Dallas next week
President Barack Obama will travel early next week to Dallas, the White House said on Friday.
Obama, who is in Poland for a NATO summit, will return to Washington on Sunday night, cutting short his European trip by one day and eliminating a stop in Seville, Spain, the White House said.
Earlier, Obama reacted to the killings of two black men in Louisiana and Minnesota.
"When incidents like this occur, there's a big chunk of our fellow citizenry that feels as if because of the color of their skin they are not being treated the same," he said shortly after landing in Warsaw, Poland, for a NATO summit.
"And that should trouble all of us. This is not just a black issue. It's not just a Hispanic issue. This is an American issue that we should all care about," he said.
UN chief concerned over racial disparities
Reacting to the killing of two black men in the US this week, United Nations Secretary-General Ban Ki-moon called for the United States to comprehensively address discrimination, including racial disparities in law enforcement.
Ban also condemned the killing of five police officers in Dallas, his spokesman Farhan Haq said in a statement.
Ban called for a "thorough and impartial" investigation into the deaths of the black men, Haq said.