Thousands of mostly peaceful pro-Palestinian protesters marched in Chicago on the opening day of the Democratic National Convention on Monday, in a show of anger against the Biden administration’s support for Israel in the Gaza offensive, Reuters reports.

After hours of peaceful demonstrations, dozens of protesters broke through part of the perimeter security fence, drawing riot police to the site, a Reuters witness said.

The DNC’s security team confirmed that protesters breached a portion of the fencing on the outer perimeter near the convention arena but said law enforcement personnel acted quickly and there was no threat to attendees.

Reuters witnesses saw four people detained and placed in handcuffs. Chicago police confirmed at a press conference that arrests were made but did not say how many.

Chanting intensified ahead of the fence breach, as protesters reached a neighborhood park on Chicago’s West Side and paused to amplify their calls for a ceasefire. Amid the noise, the crowd turned its frustration toward Vice President Kamala Harris, referring to the Democratic candidate as “Killer Kamala”.