At least two military facilities in Tennessee have been attacked in shootings , including a Navy recruiting building.

Chattanooga police said they were no longer looking for a gunman, though there was no word on what had happened to the suspect or suspects.

Chattanooga mayor Andy Berke said at a news conference that it was a "very terrible situation". He said there's "an officer down" at a military reserve centre.

Police have set up a command post near one of the sites.

The US Navy said in a tweet that there was a shooting at a Navy recruiting building in Chattanooga.

Law enforcement officials told recruiters at a facility seven miles away that they were also attacked by a gunman in a car. The man stopped in front of the recruiting facility, shot at the building and drove off, said Brian Lepley, a spokesman with the US Army Recruiting Command in Fort Knox, Kentucky.

The Army recruiters at the facility told Mr Lepley they were not hurt and had evacuated.

Marilyn Hutcheson, who works at Binswanger Glass just across the street from the US Naval Reserve building on Amnicola Highway, said she heard a barrage of gunfire around 11am.

"I couldn't even begin to tell you how many," she said. "It was rapid fire, like pow pow pow pow pow, so quickly. The next thing I knew, there were police cars coming from every direction."

She ran inside, where she remained locked down with other employees and a customer. The gunfire continued with occasional bursts she estimated for 20 minutes.

"We're apprehensive," Ms Hutcheson said. "Not knowing what transpired, if it was a grievance or terroristic related, we just don't know."