Keith Urban 'horrified' by alleged concert rape

Keith Urban has spoken of his horror after finding out a teenage girl was allegedly raped during one of his concerts in the US last Saturday.

The Australian country singer released a statement yesterday after news broke of the alleged sexual assault at his outdoor concert in Mansfield, near Boston.

"My team and I were horrified to learn of the events reported in Boston this past weekend and our hearts and prayers go out to all those affected," the statement read.

"This type of behaviour stands in stark contrast to the spirit of our shows."

Sean Murphy, 18, was arrested after he was photographed by fans lying on top of a 17-year-old girl he had met earlier that night.

Dozens of fans witnessed the alleged rape in plain sight in a section of the outdoor auditorium known as "the lawn", with most doing nothing to intervene.

Urban, who was unaware of the assault, posted a video after the concert specifically referencing the grassy area behind the seats at the venue.

"Gosh, up on the lawn tonight, that was nuts though," he said in a video that has since been deleted from YouTube.

"What a great night tonight."

More than 50 people were taken into protective custody at the gig, and another 46 were treated for alcohol-related illnesses.