A Democratic mayoral candidate in Kentucky’s largest city has said he is “shaken but safe” after a suspect stormed his campaign headquarters and fired a weapon point-blank at him.

Craig Greenberg, who is running for mayor of Louisville, said he was at his campaign office with four colleagues when a man appeared in the doorway with a weapon.

“When we greeted him, he pulled out a gun, aimed directly at me and began shooting,” Mr Greenberg said at a news conference several hours after the attack.

The person closest to the door managed to get the door shut, he said, then the staff barricaded the door and the suspect fled.

“Despite one bullet coming so close that it grazed my sweater and my shirt, no one was physically harmed,” Mr Greenberg said.

“We are shaken but safe.”

Mr Greenberg said he had not yet seen his family, though he had spoken with his wife on the phone after the attack and was anxious to get home. While he declined to talk about the assailant’s possible motive, he made a point to connect his experience to gun violence.

“Today is not a day for politics, but it’s not lost on me that the violence my staff and I experienced today is far too common in our city. Too many Louisville families have experienced the trauma of gun violence,” he said.

Kentucky governor Andy Beshear condemned the attempt on Mr Greenberg’s life and called for swift action to punish the perpetrator.

“The person who’s done it needs to be prosecuted to the fullest extent of the law,” he said. “And if this has anything to do with a political race, my God, if you disagree with someone you vote against them.”

Police responded to the scene after reports came in of an “active aggressor”. A suspect was apprehended outside the building shortly after the shooting, Louisville Metro Police Chief Erika Shields said.

She agreed that Mr Greenberg appeared to have been the target of the attack.

He would not comment on the specifics of the attack or whether he recognised the suspect.

Police say the motive remains under investigation. The suspect appeared to have acted alone.

Mr Greenberg launched his mayoral campaign last year and has built a big fundraising lead in a crowded race to succeed outgoing mayor Greg Fischer.

The Democrat, a prominent businessman, worked as chief executive of 21c Museum Hotels and also served on the University of Louisville board of trustees for a couple of years.

Charles Booker, a Louisville Democrat running for the US Senate, called the shooting a “critical reminder of the work we must do to realise true community safety”.