By SOPHIA TAREEN, JOEY CAPPELLETTI and LEA SKENE Associated Press

CHICAGO (AP) — Dozens of protesters broke through a security fence near the site of the Democratic National Convention on its opening day Monday as thousands took to the streets to voice their opposition to the war in Gaza.

Families with babies in strollers, students, elected leaders and others holding signs and flags joined the march to the United Center, where the convention is being held, to call for a ceasefire in the Israel-Hamas war. As the larger group marched peacefully, a few dozen who broke away tore down pieces of the security fence.

Several protesters who had managed to get through the fence were detained and handcuffed by the police. Officers put on gas masks as some protesters tried to bring down a second fence set up in front of police. Authorities said the inner security perimeter surrounding convention site was not breached and there was no threat to those attending the convention.

Chicago Police Superintendent Larry Snelling said some of the protesters who took down the fence threw water bottles and other items at police. Police de-escalated the situation without using their batons or chemicals, he said.

“When you have people infiltrate a crowd and they want to commit acts of violence, vandalism we are going to stop them,” said Snelling, who walked in a group of officers ahead of the protesters Monday. “We are not going to tolerate anyone who is going to vandalize things in our city.”

Members of the crowd chanted “End the occupation now” and then “The whole world is watching!” just as anti-Vietnam War protesters did during the infamous 1968 convention in Chicago when police clashed with protesters on live television. Families gathered on their porches and outside their doors as protesters marched by. Some children wore keffiyeh, blew bubbles or held “free fist bumps” signs.

The march happened just as President Joe Biden, who has been the target of intense criticism from pro-Palestinian groups, including the marchers, was doing a walk-through of the largely empty United Center. Biden was scheduled to address the party in the evening.

“Biden, you can’t hide. We charge you with genocide,” the marchers chanted amid the beating of drums. They also referred to him as “Genocide Joe” and lodged similar chants at Vice President Kamala Harris.

Protesters said their plans have not changed since Biden left the race and the party quickly rallied behind Harris, who will formally accept the Democratic nomination this week. Activists said they were ready to amplify their progressive message before the nation’s top Democratic leaders.

“People are dying,” said Cameron Benrud, a 25-year-old high school special education teacher from Minneapolis. He drove five hours to attend the rally at Union Park to call on Democratic officials to halt funding to Israel.

“I’m from little old Minnesota, and you feel kind of powerless… You gotta do something,” he said.

Mayor Brandon Johnson said authorities were well prepared. “The city of Chicago is really good at things like this,” he told a news conference. “We are ready.”

Organizers had hoped at least 20,000 people would take part in Monday’s rally and march, but it appeared that only a few thousand were present, though city officials declined to give a crowd estimate.

“We’re proud of the turnout, especially considering the degree of the repression from the city,” said organizer Faayani Aboma Mijana.

The Chicago area has one of the largest Palestinian communities in the nation, and buses were bringing activists from all over the country.

Taylor Cook, an organizer with the Freedom Road Socialist Organization, traveled from Atlanta for the march. Cook said the group was pushing all Democrats to call for an end to aid to Israel, with a particular focus on Harris.

“We’re saying to Kamala, she has been complicit in this. People think it’s just Joe Biden, but she is vice president,” Cook said. “So we’re saying, you need to stop if you want our vote.”

Medea Benjamin, who traveled to Chicago from Washington, D.C., with a women-led group of protesters calling for peace, said she was shocked that the Biden administration recently approved an additional $20 billion in weapons sales to Israel.

“There’s an incredible discrepancy in what people are calling for in this country and what the administration is doing,” she said ahead of the rally in Union Park. “We’re so disgusted by this.”

Pro-Palestinian supporters descended on the park, west of the Loop business district, for the rally.

Prior to the march, independent presidential candidate Cornel West addressed the crowd, which welcomed him with cheers.

“This is not about some Machiavellian politics or some utilitarian calculation about an election,” he yelled into a microphone. “This is about morality. This is about spirituality.”

Around 40 pro-Israel supporters walked around the park during the rally. Remaining mostly silent while waving Israeli flags, they were accompanied by about 20 police officers on bicycles. Although tensions flared at times, there were no physical altercations.

Josh Weiner, co-founder of Chicago Jewish Alliance who walked with the pro-Israel group, said their intent was to “make our presence felt.” He said the group applied for permits that were not approved by the city.

“The pro-Palestine protesters have gotten multiple permits, including a march, which seems to be a little bit weighted on one side,” Weiner said.

Coalition activists and the city have been at odds over the location of the protests and other logistics. A judge sided with the city over an approximately 1-mile (1.6-kilometer) march route, which organizers argued was not big enough for the expected crowds.

Not a single speaker or spectator showed up to a speakers’ stage offered by city officials near the United Center. Eight groups with progressive agendas had signed up for 45-minute speaking slots on Monday. On other days, some conservative groups, including the Illinois Policy Institute think tank, have plans to speak.

In the afternoon, the Philadelphia-based Poor People’s Army, which advocates for economic justice, set up in Humboldt Park on the city’s northwest side before marching more than 3 miles (5 kilometers) to the United Center.