Riot police in New York City fought with protesters who marched across Brooklyn Bridge to celebrate Martin Luther King Day on Monday.
A Black Lives Matter demonstration began peacefully in Brooklyn on Monday afternoon to mark the annual commemoration.
Several hundred people then crossed into Manhattan.
As night fell, they were told to clear the area but some refused. CBS reported that 30 people were arrested, and ten police officers were injured including a captain struck on the head with a bottle.
Freelance video journalist Leeroy Johnson filmed the police rushing the crowd, attempting to force them from the road.
In another picture a man could be seen being carried away by the police.
'They definitely charged multiple times,' said Egypt Staley, 22, of Washington Heights.
He told the New York Daily News: 'Some people were just being grabbed off the sidewalk. Some people were not even facing them.
'They surrounded us. People were trying to leave. Some people were like, 'How can I even leave?' '
Helen Guzman, 30, told the paper: 'They were really violent. Cops were pushing, shoving folks, pummeling people, tackling them.'
The area was all quiet by around 10pm, according to social media.
Monday's unrest came four days after New York's attorney general sued the New York Police Department for its handling of the George Floyd protests in the spring.
Letitia James, the attorney general, called the rough treatment of protesters against racial injustice part of a longstanding pattern of abuse that stemmed from inadequate training, supervision and discipline.
James' lawsuit includes dozens of examples of alleged misconduct during the spring demonstrations in the wake of Floyd's police killing, including the use of pepper spray and batons on protesters, trapping demonstrators with a technique called kettling and arresting medics and legal observers.
'We found a pattern of deeply concerning and unlawful practices that the NYPD utilized in response to these largely peaceful protests,' James said at a news conference announcing the lawsuit.
James, a Democrat, was tasked by Gov. Andrew Cuomo with investigating whether NYPD officers used excessive force to quell unrest and enforce Mayor Bill de Blasio's nightly curfew.
She issued a preliminary report in July that cited a 'clear breakdown of trust between police and the public.'
James is seeking reforms including the appointment of a federal monitor to oversee the NYPD's policing tactics at future protests and a court order declaring that the policies and practices the department used during the protests were unlawful.
The lawsuit in federal court named the city, de Blasio, police Commissioner Dermot Shea and Chief of Department Terence Monahan as defendants.
James criticized de Blasio for saying the use of kettling was justified and Shea for saying that the NYPD 'had a plan which was executed nearly flawlessly' when officers aggressively cracked down on protesters on June 4 in the Bronx.
In June, at the height of the protests, de Blasio was accused of misleading the city when he told reporters that he personally saw 'no use of force around peaceful protests,' even after officers had been caught on video moving on demonstrators without provocation and bashing them with batons.
De Blasio said he met with James on Wednesday and that they share the goal of pushing for major police reforms, such as implementing recommendations in previous reports on the NYPD's protest response.
De Blasio, also a Democrat, said however that he did not agree a lawsuit was the solution.
'A court process and the added bureaucracy of a federal monitor will not speed up this work,' de Blasio said. 'There is no time to waste and we will continue to press forward.'
John Miller, the NYPD's deputy commissioner of intelligence and counterterrorism, said the department is committed to reform but that James' lawsuit 'doesn't seem to meet the standard for a federal monitor, and it doesn't seem to illustrate a pattern and practice' as required.
The head of the city's largest police union blamed a 'failure of New York City's leadership' for sending officers 'to police unprecedented protests and violent riots with no plan, no strategy and no support.'
'They should be forced to answer for the resulting chaos, instead of pointing fingers at cops on the streets and ignoring the criminals who attacked us with bricks and firebombs,' Police Benevolent Association President Pat Lynch said.
James' lawsuit is the second major legal action to stem from the NYPD's handling of the protests.
In October, the New York Civil Liberties Union and the Legal Aid Society sued the city on behalf of protesters who say they were assaulted and abused by police.
Andrew Smith, a black man who was seen on video getting pepper sprayed in the face by a white officer who'd tore down his facemask, said that officer 'showed the world the inadequate training, the violent racist culture of the NYPD when he attacked me when my hands were high up in the air.'
A civil rights organization and a city watchdog agency have also criticized the department's actions.
Human Rights Watch issued a report in November on the Bronx crackdown and the city's inspector general issued a report in December that found that the NYPD was caught off guard by the size of the protests and resorted to aggressive tactics that stoked tensions and stifled free speech.
Mark Winston Griffith, a spokesperson for the advocacy group Communities United for Police Reform applauded the lawsuit, saying: 'NYPD violence against protesters is a long-standing problem and it's a credit to Attorney General James that she's using the power of her office to challenge the systemic lack of accountability for this violence.'
In a joint statement, the NYCLU and Legal Aid Society said: 'We hope this will be the beginning of a serious reckoning over police violence and militarized use of force against protesters, especially people of color, and a check on the impunity many officers have come to see as their right.'