The baby, whose full name will be Kingston James McGregor Rossdale, weighed 7.5 pounds (3.4 kg) at birth, spokesman Dave Tomberlin said. He gave no further details.

Us Weekly magazine reported the baby was delivered by Caesarean section at Cedars-Sinai Medical Centre in Los Angeles, after which Rossdale walked out of the operating room to announce the news to waiting relatives.

One witness outside the hospital who saw the couple arrive on Friday morning told the magazine that Stefani showed up "wearing her signature red lipstick and looked so excited".

Stefani, 36, who played Hollywood actress Jean Harlow in Martin Scorsese's film epic The Aviator, announced her pregnancy last December during the final concert stop of her solo tour, saying, "This is the end of a huge chapter for me."

She and Rossdale, 38, met in 1995 when Stefani's band No Doubt opened for Rossdale's former band, Bush. The couple married in September 2002.