Thousands of protesters marched toward the site of the Democratic National Convention on its opening day to voice their opposition to the war in Gaza, as Chicago officials said they were committed to keeping the demonstrations peaceful.

Protesters said their plans have not changed since US President Joe Biden left the race and the party quickly rallied behind Vice President Kamala 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.

“We have to play our part in the belly of the beast to stop the genocide, to end U.S. aid to Israel and stand with Palestine,” said Hatem Abudayyeh, a spokesman for the Coalition to March on the DNC, which includes hundreds of organisations.

Protesters marched along a mile-long route ending at a park near the United Centre, where the convention is being held, 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.

“Biden, you can’t hide. We charge you with genocide,” they chanted amid the beating of drums.

“Harris, you can’t hide. We charge you with genocide.”

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.”

Organisers said they hoped the turnout for Monday’s rally and march would be at least 20,000 people.

It appeared a few thousand were present at the start of the march, though Chicago city officials declined to give a crowd estimate.

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

Medea Benjamin, who travelled to Chicago from Washington DC with a women-led group of protesters calling for peace, said she was shocked that the Biden administration recently approved an additional 20 billion dollars 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.”

Activists say they learned lessons from last month’s Republican National Convention in Milwaukee. They expect bigger crowds and more robust demonstrations in Chicago.

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”.

Mr Weiner 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,” Mr Weiner said.

Protester issues also include climate change, abortion rights and racial equality, to name a few, but many agree that pressing for an immediate ceasefire in the Israel-Hamas war is the top message of the demonstrations.

They have likened it to the Vietnam War of their generation.

Chicago, which has hosted more political conventions than any other US city, has been unable to escape comparisons to the infamous 1968 convention where police and anti-Vietnam War protesters violently clashed on live television.

Some businesses boarded up their windows as a precaution, and county courts said they would open more space in case of mass arrests. Chicago police say officers have undergone extensive training on constitutional policing and de-escalation tactics.