US gun crime: Four dead, multiple people shot at Tulsa, Oklahoma hospital

A man armed with a rifle and a handgun opened fire inside a medical building in Tulsa, Oklahoma, killing four people, according to police, in the latest of a series of mass shootings in the United States.

Police Deputy Chief Jonathan Brooks confirmed the number of dead and said the shooter also was dead, apparently from a self-inflicted gunshot wound.

It was unclear what prompted the deadly assault. However, the unidentified gunman fired both a handgun and a rifle during the attack, Brooks said.

Authorities responded to a call about a man who was armed with a rifle at the Natalie Medical Building, a physicians' office building on the St Francis Hospital campus, according to an earlier Facebook post from the Tulsa Police Department.

Police on the scene of a shooting at medical buildings in Tulsa, Oklahoma. Police say four people, including the shooter, are dead. Photo / Tulsa Police Department

"Officers are currently going through every room in the building checking for additional threats," police said in a Facebook post. "We know there are multiple injuries, and potentially multiple casualties."

Police responded to the call three minutes after dispatchers received the report and made contact with the gunman one minute later, Brooks said.

Police Captain Richard Meulenberg also said multiple people were wounded and that the medical complex was a "catastrophic scene."

St Francis Health System locked down its campus because of the situation at the Natalie Medical Building. The Natalie building houses an outpatient surgery centre and a breast health centre.

Tulsa resident Nicholas O'Brien, whose mother was in a nearby building when the shooting occurred, told reporters that he rushed to the scene.

"They were rushing people out. I don't know if some of them were injured or just have been injured during the shooting, but some of them couldn't walk very well. But they were just kind of wobbling and stumbling and getting them out of there," he said.

"I was pretty anxious. So once I got here and then I heard that she (his mother) was OK, the shooter had been shot and was down, I felt a lot better. It still is horrible what happened," O'Brien said.

The shooting comes eight days after an 18-year-old gunman armed with an automatic rifle burst into Robb Elementary School in Uvalde, Texas, and killed 19 children and two teachers before being fatally shot himself. It's more than two weeks after shooting at a Buffalo supermarket by a white man who is accused of killing 10 black people in a racist attack.

The recent Memorial Day weekend saw multiple mass shootings nationwide, even as single-death incidents accounted for most gun fatalities.

- AP