A large protest in Brooklyn against Israel’s military offensive in Gaza erupted into a chaotic scene on Saturday, as the police arrested dozens of pro-Palestinian demonstrators and at times confronted them violently.

In videos posted on social media, officers can be seen punching at least three people who were prone on the ground at the demonstration in the Bay Ridge neighborhood. The aggression was corroborated by eyewitnesses. Another protester who was filming the police was tackled and arrested.

At least 34 people were arrested, according to a senior law enforcement official who spoke on condition of anonymity to discuss a developing situation. The charges they face were unclear early Sunday morning.

“I saw police indiscriminately grabbing people off the street and the sidewalk,” said Nerdeen Kiswani, founder of Within Our Lifetime, an activist group led by Palestinians who organized the demonstration. “They were grabbing people at random.”

In recent years, Within Our Lifetime has put on an annual mid-May rally in Bay Ridge, a neighborhood with a large Arab population, to commemorate what Palestinians call the Nakba, or “catastrophe” — when hundreds of thousands of Palestinians were forced from their homes during the war that led to Israel’s founding in 1948.