NEW YORK (CBSNewYork/AP) — Some activists and elected officials are criticizing the NYPD’s handling of protests over the death of a Baltimore man critically injured in police custody.

The group claimed Thursday that the NYPD was overly aggressive and at times violent.

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NYPD Commission Bill Bratton said 143 people were arrested Wednesday night during a rally and march over the death of Freddie Gray. Gray suffered a severe spinal injury in the custody of Baltimore police. He later died.

Bratton said Thursday police would be “more assertive” in dealing with demonstrators who try to block roads or bridges than they were during December protests in the wake of the Eric Garner grand jury decision.

“We will be much faster to make arrests if, in fact, they attempt to move in those directions,” Bratton told reporters, including 1010 WINS’ Al Jones.

Mayor Bill de Blasio insisted Thursday that there was not a fundamental change in police treatment of demonstrators.

He told reporters, including WCBS 880’s Rich Lamb and 1010 WINS’ Carol D’Auria, that police made it clear with sound trucks and pamphlets where protesters could march.

De Blasio issued a blunt warning: “When the police give you instruction, you follow the instruction. It’s not debatable. And I’m saying this as someone who has been at these protests and recognize when the police say ‘stay to the sidewalk,’ it means stay to the sidewalk. And that has to be respected.”

But two local lawmakers and some marchers claim the NYPD went too far, CBS2’s Alice Gainer reported.

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“I watched a brother who was trying to get from the street back onto the sidewalk being taken down for no reason and then put into an arrest car,” said Assemblyman Michael Blake, D-Bronx. “I saw one sister who was sitting off doing absolutely nothing and then all of a sudden was hit in the head with a baton.”

Protesters first rallied in Union Square, where they chanted “No justice, no peace!” and “Hands up, don’t shoot!”

Then a group of protesters spilled into the street, shutting down the outbound Holland Tunnel, the West Side Highway and several other city streets as they marched.

The mayhem in Manhattan spread to Herald Square, Times Square and Columbus Circle, 1010 WINS’ John Montone.

The NYPD says it has an obligation to keep all New York City residents safe, including drivers and other pedestrians.

“You have the right to protest,” Bratton said. “We’ll work with you to protest as much as you want, but when you start having a very significant adverse impact on everybody else’s lives, you have to be concerned with that as well.”

No serious injuries were reported, but a commanding officer from the NYPD 13th Precinct suffered minor injuries when he was hit with a flying object near Union Square, police said.

Word is there is another even larger rally being planned for Friday night. The mayor is urging those who attend to listen to police so they can protest without incident.

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