Addressing a July 4 barbecue for military families at the White House, Biden said he was confident the US could pull through what he acknowledged were "unsettling" times.

"The economy is growing, but not without pain. Liberty is under assault, assault both here and abroad," Biden said.

"In recent days, there has been reason to think that this country is moving backward, that freedom has been reduced, that rights we assumed were protected are no longer."

Biden was referring to a rapid succession of Supreme Court rulings that overturned the 50-year-old federal right to abortion, expanded gun rights for people wishing to bear them in public and limited the government's ability to fight climate change.

"I know it can be exhausting and unsettling, but tonight, I want you to know that we're going to get through all of this," he added.

In his speech, Biden made only a passing reference to the morning shooting in Highland Park, Illinois, in which a gunman killed six people and injured two dozen more by firing on a parade with a high-powered rifle.

In an earlier statement, he had condemned the "senseless" act of violence and vowed to keep fighting what he called the epidemic of gun violence in the US.

According to the Gun Violence Archive, there have been 311 mass shootings carried out in the US so far in 2022 – including at least five other incidents on July 4.

Suspect arrest

  

Police arrested a suspect on Monday. Robert Crimo, 22, was identified as a "person of interest" and became the target of a massive manhunt across the town of Highland Park.

Firing into the holiday crowd, the shooter caused scenes of chaos as panicked onlookers ran for their lives, leaving behind a parade route strewn with chairs, abandoned balloons and personal belongings.

Emergency officials said around two dozen people, including children, were treated for gunshot injuries, with some in critical condition.

After a brief car chase, Crimo was taken into custody "without incident," Highland Park police chief Lou Jogmen told reporters.

Earlier, police had warned that he was armed and "very dangerous."

Crimo bills himself as a musician, and goes by the online moniker "Awake the Rapper."

The shooting is part of a wave of gun violence plaguing the US, where approximately 40,000 deaths a year are caused by firearms, according to the Gun Violence Archive website.

And it cast a pall over the country’s Independence Day, in which towns and cities across the country hold similar parades and people -– many dressed in variations on the US flag – hold barbecues, attend sports events and gather for firework displays.

In another July 4 shooting, two police officers were wounded when they came under fire during a fireworks display in Philadelphia, local officials said.

CBS News aired video taken from a high-rise building showing crowds fleeing in panic as fireworks burst in the sky.

Philadelphia police commissioner Danielle Outlaw said both officers had been released from hospital after receiving treatment, and that authorities were still investigating the exact circumstances of the incident.

In Highland Park, Emily Prazak, who marched in the parade, described the mayhem.

"We were getting ready to march down the street and then all the sudden waves of these people started running after, like running toward us. And right before that happened, we heard the pop, pop, pop, pop, pop, and I thought it was fireworks," Prazak told AFP.

She added: "This is the day that we celebrate our country. This is also a day that our freedom got stolen from us – because many of us residents here, in this building even, we're all locked down."