A gunman killed two people and seriously wounded another at a casino in the northern US state of Wisconsin on Saturday night before being shot dead by police, authorities said.

Police said they first received a call at 7:28 pm about a shooting at a restaurant at the Oneida Casino/Radisson Hotel and Conference Center complex near Green Bay, which is operated by the Oneida Nation.

"The suspect is deceased, the police have shot the suspect so there's no threat to the public," Lieutenant Kevin Pawlak of the Brown County Sheriff's office told reporters after midnight.

Pawlak said it appeared to be a "targeted event not a random shooting." The intended target was an employee who was not there at the time but the gunman decided to shoot some of their friends or acquaintances, he said.

The FBI were at the scene assisting with the investigation.

The seriously wounded victim was airlifted to a Milwaukee hospital, Pawlak said.