Several people were arrested by Chicago police on Monday evening when a group of protesters broke through a security cordon near the United Center at the start of the Democratic National Convention.

NBC Chicago/Telemundo: Chicago photojournalists filmed several protesters climbing over the fences at Park 578, where a demonstration authorized by city authorities was scheduled to end at 6 p.m. Chanting broke out and people banged on the fences as dozens of Chicago police officers in riot gear confronted several protesters.

One of the seven protests planned through Thursday began at 3015 W Division Street and led to the intended end point, Park 578. Although the protest was organized by the Poor People’s Human Rights Campaign, it was not clear whether the protesters who clashed with police were affiliated with the organization.

A total of 264 groups said they would participate in peaceful demonstrations. Most of them called for Palestinian rights, an end to the Gaza war and a reduction in US aid to Israel. Other groups represented a hodgepodge of left-leaning causes: climate activists, socialists, anti-racist organizations, queer and trans rights groups.

Chicago Police Commissioner Larry Snelling told NBC News that police would act peacefully as long as protesters were peaceful.

“If people come here to peacefully protest and exercise their First Amendment rights, our officers will not only allow them to do so, but will protect them while doing so,” Snelling said in an interview. “But what our officers will not allow is for someone to come into our city and destroy it. Acts of violence and vandalism will not be tolerated in this city.”