Thousands of marchers took to the streets for a mostly peaceful protest near the Democratic National Convention (DNC) on its opening day, calling for a ceasefire in Gaza and an end to US support for Israel.
But several demonstrators were arrested when dozens of them broke through a security fence around the Chicago venue.
The turnout appeared to be well below the tens of thousands that organisers had hoped for and short of the 15,000 they claimed turned out.
Later in the evening, President Joe Biden acknowledged that the protesters "out on the street have a point" in his primetime convention farewell speech.
"A lot of innocent people are being killed, on both sides," he said, adding that a US-brokered ceasefire - which has so far proved elusive - was necessary.
Protests in Chicago have highlighted divisions among Democrats over one of the most contentious issues on the left of American politics, US support for Israel’s war in Gaza.
At one point during Monday's protest, a small group of pro-Palestinian demonstrators knocked down a fence around the convention security perimeter and streamed through.
Chicago Police said the protesters did not breach an inner security fence and that the situation was quickly contained. At least four people were detained.
Many of the Gaza war demonstrators said they saw little difference between Mr Biden and his Vice-President Kamala Harris, who is formally accepting the Democratic White House nomination this week after the president dropped out of the race last month and endorsed her.
“The Democratic Party may present a new face, but its support for Israeli repression remains unchanged,” said Omar Younes, a co-founder of Jisoor, a Palestinian youth organisation in Chicago.
Another protester, Tallis George Munro, said he would definitely vote for Ms Harris and her running mate, Tim Walz, but did not want to give them a “free pass” on their support for Israel’s war in Gaza.
Mr Munro, from Cleveland, Ohio, said he was more worried about what he described as a "bigger threat" – the policies of Republican nominee Donald Trump.
"We are close to white Christian nationalism with Trump," he said. "That is the biggest problem in this country now."
Other protesters told the OceanNewsUK they would vote for Green Party candidate Jill Stein, or they would not vote at all.
The rally-goers also heard from independent presidential candidate Cornel West, a philosophy professor and left-wing activist.
"This is not about some Machiavellian politics or some utilitarian calculation about an election," he told the crowd. "This is about morality."
After months of legal wrangling over the route, protesters followed a 1.1 mile (1.8km) path around the DNC site, chanting slogans including "No justice, no peace, US out of the Middle East" and "Kamala Harris is a cop, all this violence has to stop" – a reference to the vice-president's career as a prosecutor and California attorney general.
The demonstrators also chanted "from the river to the sea, Palestine will be free".
This refers to the land between the River Jordan, bordering the occupied West Bank and Israel in the east, to the Mediterranean Sea in the west. Anti-semitism monitors say it calls for the destruction of Israel but pro-Palestinian groups deny the slogan is hateful.
Earlier in the day, a small contingent of pro-Israeli counter-protesters briefly rallied on the edge of Union Park, where the pro-Palestinian march began and ended.
The march drew people from neighbouring states and further afield. Karyna Lemus attended as a member of the Colorado Springs People’s Coalition.
She said she’s been involved in the Palestinian rights movement for decades.
“I hope they hear us inside,” she said of the DNC delegates.
Protests will continue for the rest of the week during the convention.
The Israeli military launched a campaign in Gaza to destroy Hamas in response to an unprecedented attack on southern Israel on 7 October, during which about 1,200 people were killed and 251 taken hostage.
More than 40,000 people have been killed in Gaza since then, according to the territory's Hamas-run health ministry.
