Gunfire erupted at a Fourth of July parade route in the wealthy Chicago suburb of Highland Park on Monday, the Lake County Sheriff's office said, with a local TV station saying at least two people were killed.

"STAY OUT OF THE AREA - allow law-enforcement and first responders to do their work," the sheriff's department said on Twitter, adding that deputies were assisting Highland Park police.

WGN TV, citing unidentified law enforcement sources, said at least two people were killed and multiple people were injured. The suspect remains at large, WGN reported, citing a law enforcement source.

U.S. Representative Brad Schneider, whose district includes Highland Park, said he and his campaign team had been gathering at the start of the parade when the shooting started.

"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," Schneider said on Twitter. "Enough is enough!"

The parade was suddenly halted when shots were fired about 10 minutes after it began, sending hundreds of people running for safety, the Chicago Sun-Times reported.

People fled the scene upon hearing several loud bangs, CBS 2 television of Chicago reported, citing a producer who was at the parade.

"Everyone was running, hiding and screaming," CBS 2 Digital Producer Elyssa Kaufman said, the channel's website reported.