At least six people have died and 24 people were wounded after a shooting at a July 4 parade near Chicago, police said.

The shooting, in Highland Park, disrupted the annual parade around 10 minutes after it began at 10am local time (4pm in the UK).

Highland Park Police initially said five people were killed and 19 people were taken to hospital.

Lake County major crime taskforce spokesman Christopher Covelli said at a news conference that the gunman apparently opened fire on parade-goers from a rooftop using a rifle that was recovered at the scene.

Six people dead in Illinois shooting at July 4 parade

The police said the authorities were still searching for the suspect and it is being treated as an active incident.

Brad Schneider, a Congressman who represents the district, tweeted: "Today a shooter struck in Highland Park during the Independence Day parade. My campaign team and I were gathering at the start of the parade when shooting started. My team and I are safe and secure. We are monitoring the situation closely and in touch with the Mayor."

He then added: "Hearing of loss of life and others injured. My condolences to the family and loved ones; my prayers for the injured and for my community; and my commitment to do everything I can to make our children, our towns, our nation safer. Enough is enough!"

The mayor of Highland Park, Nancy Rotering, said the festival had been cancelled and asked people to avoid the downtown area.

Mayor Rotering said: “This morning at 10.14 our community was terrorised by an act of violence that has shaken us to our core.

“Our hearts go out to the families of the victims at this devastating time.

“On a day that we came together to celebrate community and freedom, we are instead mourning the tragic loss of life and struggling with the terror that was brought upon us.”

Highland Park Police initially said in a statement that five people had been killed and 19 people were taken to hospital, but those numbers were revised soon after at the news conference.

The tragedy comes after President Joe Biden addressed Americans during the July 4 celebrations. 

Taking to Twitter, the 46th president wrote: "The Fourth of July is a sacred day in our country – it's a time to celebrate the goodness of our nation, the only nation on Earth founded based on an idea: that all people are created equal. Make no mistake, our best days still lie ahead."