Compston, who lives in the Nevada city with his family, was filmed on stage at an event held by the North American Celtic Supporters Federation (NACSF).

In a video widely shared on social media, the crowd sings about the "Irish Republican Army", adding: "It's the I, I, I, IRA."

As they sing "IRA", Compston is seen appearing to lift his left arm into the air.

In a statement, the 38-year-old Scot, who plays Steve Arnott in the police drama, said he "unequivocally did not sing ANY sectarian songs".

He added: "I've worked in Belfast too long (where Line of Duty is filmed) to see damage done to think this stuff is a laugh."

Compston also referred to Daniel Boone's 1972 hit track, Beautiful Sunday, which is frequently played at Celtic Park.

He said: "If it was an IRA song and I was onstage bobbing along I would understand the story.

"But I'm pretty sure Daniel Boone had nothing more than Beautiful Sundays in mind when he wrote the song and that's what I was singing."

Dave Scott, director of anti-sectarian charity Nil by Mouth, told The Scottish Sun it was a "pretty depressing spectacle".

He added: "Those involved in the IRA chanting need to take a long hard look at themselves in the mirror. These are adults - not children who might not know any better.

"The worst thing? Children and young people could see this and now think this is totally acceptable behaviour."

There were some scathing comments on social media. One person said it was "sickening", while another said it was "utterly unacceptable".