Breaking: Five shot, one killed, at Washington DC gym - ABC News & Headlines – Australian Broadcasting Corporation

Dozens of emergency crews were sent to the scene in the Logan Circle neighbourhood. (AP: Tom Brenner)

One person has been killed and four others injured after a man opened fire inside a gym in a central Washington DC neighbourhood.

Police said the suspected gunman had been located with a gunshot wound, believed to be self-inflicted, after he barricaded himself inside a nearby apartment building.

Negotiators had been communicating with the man for more than an hour before forcing their way inside the seventh-floor apartment. His condition is unknown.

The area is about 1.5 kilometres north of the White House.

Panic spread through the area after the man opened fire in the Vida gym on 15th St Northwest, in the Logan Circle neighbourhood, about 8am, local time.

Some officers were seen on nearby rooftops as local and federal law enforcement responded to the shooting. (AP: Julia Demaree Nikhinson)

Local area councillor Brooke Pinto said she believed the victim was targeted by the suspect over an apartment dispute.

Washington DC's acting police chief, Jeffery Carroll, earlier said the suspect had been involved in a "conflict" with the home-owners' association of the building. 

"The suspect, in fleeing the scene, also shot others," Councillor Pinto told local television. 

Mr Carroll said victims were shot at multiple locations.

One of the victims was in a critical condition, police said. The three other surviving victims had non-life-threatening injuries.

Gym-goers ran into a nearby bagel shop to shelter after the man started shooting, witnesses told reporters at the scene.

One woman said she was on a treadmill when she heard a gunshot and saw a victim on the ground.

"It was, like, chaos. It was horrific," said said.

"We exited and then had to tell the police what was happening, and that's when more shots were happening, and that's when we all ran into Call Your Mother [bagel shop] around the corner," she said.

Buildings in the area were placed in lockdown as authorities surrounded the apartment complex and negotiated with the suspect.

Dozens of police vehicles were at the scene, which was cordoned off during the morning peak.

Members of the National Guard, who have been present in Washington DC as part of a crime crackdown ordered by US President Donald Trump, were also at the scene.