Singer Bobby Farrell of the 1970s European chart-topping group Boney M has been found dead in his hotel bed while on tour in Russia, his agent said. He was 61.

Farrell performed as scheduled in St Petersburg on Wednesday night, but complained of breathing problems before and after his show, said the agent, John Seine. He had been due to fly to Rome on Thursday for a television show.

Seine said the cause of death was not known, but Farrell had suffered health problems off-and-on for 10 years. He said he was found dead by hotel staff on Thursday after he failed to respond to a wake-up call.