TULSA, June 1 (CNA) - At least five people were dead after a man armed with a rifle opened fire on Wednesday (Jun 1) inside a medical building in Tulsa, Oklahoma, in the latest of a series of mass shootings in the United States.

Tulsa Police said on Twitter that five people were dead, including the gunman, in an "active shooter situation" at the Natalie Building on the St Francis Hospital campus.

The gunman died apparently of a self-inflicted wound, Tulsa's deputy police chief Jonathan Brooks told reporters outside the hospital campus.

He said that police were trying to determine the man's identity, but said he was aged between 35 and 40.

Captain Richard Meulenberg told ABC News that Tulsa Police received a call about a man with a rifle on the second floor of a building on the medical campus and that "it turned into an active shooter situation".

By the time officers arrived on the scene, "they found a few people have been shot. A couple were dead at that point", Meulenberg said.

Brooks said officers arrived on the scene three minutes after receiving a call about the shooting and made contact with the victims and the suspect five minutes later. The gunman was armed with a rifle and a handgun.

"I also want to express our community's profound gratitude for a broad range of first responders who did not hesitate today to respond to this act of violence," Tulsa Mayor GT Bynum said.

The shooting occurred on the second floor of the campus's Natalie Building, which contains doctor's offices and an orthopaedic centre.

Eric Dalgleish, another Tulsa deputy police chief, said he believed the victims included employees and patients.

The White House said President Joe Biden has been briefed on the shooting and offered support to state and local officials in Tulsa, a city of about 411,000 people that sits about 160km northeast of the capital Oklahoma City.

The Tulsa shooting follows two mass shootings in May that shocked Americans and reignited debates about gun control. Last week, a gunman killed 19 children and two teachers at an elementary school in Uvalde, Texas. Earlier in May, a shooter killed 10 people at a supermarket in Buffalo, New York.