CHICAGO (AP) — Protesters broke through a fence erected by police near the venue on Monday, the opening day of the Democratic National Convention, as thousands took to the streets to voice their opposition to the war in Gaza.

As the larger group marched, several dozen protesters tore down sections of the security fence. Some protesters, dressed in black and with their faces covered, dragged sections of the fence into a park near the United Center, where the convention is taking place.

Several protesters who managed to get through the fence were arrested and handcuffed by the police.

The authorities stated that the internal security perimeter around the congress site had not been breached and that there was no danger to the congress participants.

Members of the crowd chanted “End the occupation immediately” and then “The whole world is watching!” just as anti-Vietnam War protesters did during the infamous 1968 convention in Chicago, when clashes between police and protesters were televised. Officers donned gas masks as some protesters attempted to tear down a second fence that had been erected in front of the police.

The march came just as President Joe Biden, who has faced heavy criticism from pro-Palestinian groups, including the protesters, was walking around the largely empty United Center. Biden was scheduled to address the party that evening.

“Biden, you can’t hide. We accuse you of genocide,” the protesters chanted amid drumbeats. They also called him “Genocide Joe” and directed similar slogans at Vice President Kamala Harris.

The protesters said their plans have not changed since Biden dropped out of the race and the party has quickly rallied behind Harris, who will formally accept the Democratic nomination this week. The activists said they are ready to take their progressive message to the country’s top Democratic politicians.

“We must do our part to stop the genocide, end U.S. aid to Israel and stand with Palestine,” said Hatem Abudayyeh, a spokesman for the DNC march coalition, which includes hundreds of organizations.

The heavy police presence at the march included Chicago Police Commissioner Larry Snelling, who walked in front of the protesters with a group of officers.

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

Organizers had hoped that at least 20,000 people would attend Monday’s rally and march. But when the march began, only a few thousand people appeared to be present. City officials declined to provide estimates of the number of participants.

“We are proud of the participation, especially given the extent of the repression by the city,” said organizer Faayani Aboma Mijana.

The Chicago area is home to one of the largest Palestinian communities in the country, and buses brought activists from across the country.

Taylor Cook, an organizer with the Freedom Road Socialist Organization, flew in from Atlanta to attend the march. Cook said the group is urging all Democrats to call for an end to aid to Israel, with a particular focus on Harris.

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

Medea Benjamin, who traveled to Chicago from Washington, DC with a female-led group of protesters calling for peace, said she was shocked that the Biden administration recently approved another $20 billion worth of arms sales to Israel.

“There is an incredible discrepancy between what the people of this country are demanding and what the government is doing,” she said before the rally in Union Park. “That disgusts us so much.”

Pro-Palestinian supporters flocked to the rally in the park west of the Loop business district.

Before the march, independent presidential candidate Cornel West gave a speech to the crowd, which greeted him with cheers.

“This is not about Machiavellian politics or utilitarian electoral calculations,” he yelled into a microphone. “This is about morality. This is about spirituality.”

During the rally, about 40 pro-Israel supporters walked through the park. They remained mostly silent and waved Israeli flags. They were accompanied by about 20 police officers on bicycles. Although tensions arose at times, there were no physical confrontations.

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

“The pro-Palestinian protesters have received several permits, including one for a march, although it seems to be a little one-sided,” Weiner said.

Snelling praised police and march organizers for their peaceful protest Sunday night, which promoted abortion, LGBTQ+ rights and an end to the Gaza war. Chicago police said two people were arrested for resisting police and property damage.

“Look, it’s simple. The Chicago Police Department is here to protect everyone in this city,” Snelling said. “What we do not tolerate is intimidation. We do not tolerate violence.”

Protesters’ issues include climate change, abortion rights and racial equality, to name a few, but many agree that calling for an immediate ceasefire in the war between Israel and Hamas is the demonstrations’ most important message, which they have compared to their generation’s Vietnam War.

Some stores have boarded up their windows as a precaution, and district courts said they would create more space in the event of mass arrests. Chicago police say their officers have received extensive training in constitutional policing and de-escalation tactics.

Coalition activists and the city disagree over the location of the protests and other logistical issues. A judge ruled in favor of the city’s one-mile march route, which organizers said was not long enough for the expected crowds.

By early afternoon, not a single speaker or audience member appeared on the podium provided by the city government near the United Center. Eight groups with a progressive agenda had signed up to speak for 45 minutes on Monday. On other days, some conservative groups, including the Illinois Policy Institute think tank, have scheduled talks.

Also on Monday, the Philadelphia-based Poor People’s Army, which advocates for economic justice, planned to appear in Humboldt Park in the city’s northwest area, where it would host events with third-party presidential candidates Jill Stein and West, as well as a three-mile march.