The first day of the Democratic National Convention got off to a tense start Monday as anti-Israel demonstrators marched outside the United Center, clashing with police officers and breaching part of a fence. 

The moment came after thousands of protesters marched toward the convention, shouting incendiary slogans to signal their opposition to Israel’s ongoing war with Hamas in the Gaza Strip. 

As the crowd neared the United Center, dozens of protesters broke through a fence set up by police. Officers put on gas masks as some members of the crowd tried to bring down a second fence set up in front of police, who yelled at protesters to get back. 

More police officers descended on the area of the breached fence to repair it to its original state. 

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"Demonstrators breached a portion of anti-scale fencing along the Democratic National Convention’s outer perimeter near the United Center on Aug. 19. Law enforcement personnel were immediately on-scene and contained the situation. At no point was the inner perimeter breached, and there was no threat to any protectees," the DNC Public Safety Joint Information Center said in a statement. 

"The National Special Security Event plan employs a multi-layered approach. Each NSSE plan is unique and includes multiple layers. One of these redundancies include the outer perimeter fence, which was erected to prevent entry into the inner perimeter. The Chicago Police Department remains on-scene and is working to clear the area."

Protesters shouted "quit your job" and "shame" at the officers. Marchers also directed chants at President Biden with: "Biden, you can't hide. We charge you with genocide." They also referred to him as "Genocide Joe" and lodged similar chants at Vice President Kamala Harris.

President Biden, who has been the target of intense criticism from anti-Israel groups, is scheduled to address the party Monday evening.

Protesters said their plans have not changed since Biden left the presidential race and the party quickly rallied behind Harris, who will formally accept the Democratic nomination this week. 

Earlier Monday, protesters marched along a mile-long route ending at a park near the United Center, as hundreds of police officers lined the streets. The heavy police presence at the march included Chicago Police Superintendent Larry Snelling, who walked in a group of officers ahead of the protesters.

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 when the march began.

The Associated Press contributed to this report.