Kentucky police detain suspect after ‘assassination attempt’ of candidate

Police in Kentucky have detained a person suspected of a Monday morning "assassination attempt" on a Democratic party candidate for Louisville city mayor.

The Louisville Metro police chief Erika Shields said at a lunchtime press conference that the unidentified shooter entered Craig Greenberg's fourth-floor suite in a downtown office building at about 10.15am and fired multiple shots.

Neither Greenberg, who is running for his party's nomination for city mayor in the upcoming Democratic primary, nor any of his staff were struck, Shields said, although Greenberg's clothing was nicked by a round.

Greenberg tweeted that he and his campaign team were safe and uninjured, and that he planned to give an update later. Television footage showed Greenberg and several colleagues being led from the building by a heavily armed Swat team.

The person in custody was detained near the building after officers matched their appearance to descriptions by witnesses, according to Shields.

"We have no known motive at this time. We also have no reason to believe that this individual was acting anything but alone," Shields said.

"Until we can determine what the motivating factors were, we are going to keep an open mind and proceed with an abundance of caution and concern for many of our community members. Mr Greenberg is Jewish, so there's that. We don't know if it's tied to the candidate's politics or if we are dealing with someone who has mental issues or is venomous."