A report in The Los Angeles Times said Houston had behaved erratically during an appearance on Thursday at a rehearsal for a Grammy awards party. Although she greeted people with a warm smile, she appeared disheveled, with mismatched clothes and dripping-wet hair, the paper said.

The singer flailed her hands frenetically as she spoke, skipped around the ballroom in a childlike fashion and wandered aimlessly about the lobby, according to the report.

Davis, who had been the diva's longtime mentor, went ahead with his annual concert at the hotel and dedicated the evening to Houston. He asked for a moment of silence, while a photo of the singer, hands wide open, looking to the sky, appeared on the screen.

After bursting on to the scene in the US in the 1980s, Houston went on to become one of the world's biggest R&B stars, with hits including I Have Nothing, All At Once and Get It Back.

The singer performs Until You Come Back to Me during the 26th annual American Music Awards at the Shrine Auditorium in Los Angeles. [Kevork Djansezian / AP]