Cranberries singer Dolores O'Riordan has pleaded guilty to headbutting and spitting at a garda following an alleged air rage incident, a court has heard.

She told officers during her arrest at Shannon Airport on 10 November last year that she was an "icon" and the "Queen of Limerick".

Ms O'Riordan, 44, who has since been diagnosed as suffering bipolar disorder, admitted four offences including assault and obstructing a garda during the incident following a flight from New York's JFK airport.

Ennis District Court was told she accused a garda officer of groping her and sexually assaulting her during the arrest, a claim which has since been retracted.

The court heard Ms O'Riordan, who doctors have suggested was suffering hypomania, sleep deprivation and paranoia at the time of the incident, threatened to sue arresting officers.

She also told them she paid their wages when they attempted to take her out of first class after her flight landed at 4.45am.

In evidence read to the court, Inspector Tom Kennedy said the singer-songwriter's behaviour was at first erratic, then unruly, irate, threatening, irrational and aggressive.

"Ms O'Riordan was very belligerent," he told the court.

"She said 'you are not going to arrest me. I am an icon. I'm the Queen of Limerick, I pay my taxes, I pay your wages. I'm going to sue you'."

Alcohol was not a factor, the court was told.

Ms O'Riordan did not give evidence in person. She was supported for the hearing by her mother Eileen and one of her brothers.

Judge Patrick Durcan ordered Ms O'Riordan to write letters of apology to all those affected in the incident while he considers sentencing.

The 44-year-old mother of three children aged 18, 14 and 10, who now lives in New York and is back working in the music business, will be sentenced at a date to be fixed next year.

With an address at Friarstown, Kilmallock, Co Limerick, the singer is renowned for her distinctive singing voice.

She separated from her husband in the year before the incident, the court was told.

Ms O'Riordan's solicitor Bill O'Donnell did not contest any of the evidence given to the court and said the marriage break-up put her under huge emotional stress.