In an aggressive response designed to tamp down early signs of unrest, the police arrested 143 people in Manhattan on Wednesday night as protesters marched in a show of solidarity with demonstrators in Baltimore angered by the death of Freddie Gray, an unarmed 25-year-old black man who died after being injured while in police custody this month.

Two of the protesters were arrested after assaulting officers, Police Commissioner William J. Bratton said on Thursday. One officer was injured during the demonstrations when a bottle struck him on the chin, the police said.

Some protesters stopped traffic on Houston Street in Lower Manhattan while others blocked the entrance to the Holland Tunnel. Another group marched uptown to Times Square and Hell’s Kitchen, where, later in the night, a police van filled with marchers who had been arrested sat idling in traffic.

On Thursday, some of the protest organizers criticized Mayor Bill de Blasio and Mr. Bratton for what they called a heavy-handed response.