Usher made his Broadway debut as Billy Flynn in the musical Chicago on Tuesday night (August 22) " but his stage turn was disrupted by a mobile ring tone.

Everything was going swimmingly for the star until the strains of R&B singer Cassies U & Me filled the theatre.

Ever the professional Usher carried on delivering his lines but once the performance was through the bling king bizarrely blamed the interruption on his former J Records label boss Clive Davis.

His phone was ringing in the middle of the performance, can you believe that? he spluttered. Davis, who was sitting in the audience alongside the likes of actress Penelope Cruz and soul singer Mario, denied the claims however.

Aside from the annoying phone incident and mistaken case of perpetrator, Ushers stage debut went without a hitch and he was greeted with deafening cheers as the show came to an end.

Tickets sales for Chicago have gone up 30% since the singer took over the role of Billy Flynn.

'SLJ'