On the first day of the Democratic National Convention (DNC) in Chicago, 13 people were arrested, according to Chicago police, including about ten members of a small group of agitators who broke through the outer security perimeter near the United Center.

The breach occurred during a larger protest march that was largely peaceful. About 3,500 protesters marched from Union Park to Park 578, which is north of the arena, and then returned to Union Park.

The protest, which took place on Monday afternoon, was a sign of solidarity with Palestine. The activists called for a ceasefire in the Gaza Strip and an end to US funding of Israel.

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The agitators “broke through the fence” and began to “march” inside the DNC

Chicago Police Chief Larry Snelling said the majority of protesters were peaceful, but that a small portion of “people split off and began to march when this group of individuals stayed behind and broke through the fence” surrounding the United Center at about 4:30 p.m.

“I’m not going to connect this event – the break-in – to the entire protest, because that protest was made up of people who were simply exercising their First Amendment right to free speech,” Snelling said.

“It was a brief breach,” Snelling explained. He further noted that some individuals who made it through the first line of fences attempted to break down a second barrier but were stopped by police. Some of those who breached the fence threw water bottles and other objects at police, while others in the crowd reportedly sprayed officers with pepper spray.

“We will not tolerate vandalism and violence in our city and we are ready, willing and able to respond. That is why we will continue to protect the city,” he said.

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Chicago Police Chief is proud of his handling of protesters

Snelling added: “It appears that the Chicago police are being much more aggressive against protesters during the Democratic National Convention than we have seen in recent months.”

“I couldn’t be prouder of how the Chicago Police Department responded under these circumstances. We demonstrated the training and preparation we have been doing for over a year.”

In total, 13 arrests were made in connection with the DNC protests. Snelling stated that about 10 of these arrests were directly related to the security breach. The people were charged with, among other things, trespassing, resisting and obstructing police, and aggravated assault against police officers.

“Our officers did not overreact. We were able to clear the area very quickly,” Snelling added.

Security measures around the United Center have been increased to prevent further incidents, and on Tuesday morning, emergency responders were seen erecting additional fencing around the site.

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Jeff Burnside, Democratic National Convention coordinator for the U.S. Secret Service, said: “We take a layered approach to all of our security measures and are constantly working with our state, local and federal partners to assess, make improvements and adjustments. That’s all we do.”