Kanye West and Kim Kardashian are expecting their first child.

The rapper announced at a concert on Sunday night that his girlfriend is pregnant. He told the crowd of more than 5,000 at Revel Resort’s Ovation Hall in song form: “Now you having my baby.”

The crowd roared.

Most of the Kardashian clan tweeted about the news, including Kim’s sisters and mother. Kourtney Kardashian wrote: “Another angel to welcome to our family. Overwhelmed with excitement!”

West also told concertgoers to congratulate his “baby mom” and that this was the “most amazing thing.”

The rapper and reality TV star went public in March.

Kardashian married NBA player Kris Humphries in August 2011 and their divorce is not yet finalised.

West’s Sunday night show was his third consecutive performance at Revel. He took the stage for nearly two hours, performing hits like Good Life, Jesus Walks and Clique in an all-white ensemble with two bandmates.