London, Jan 9 : Beyonce Knowles has given birth to a baby girl, but it is not yet clear whether the baby's name is Ivy Blue Carter or Blue Ivy.

According to reports, the pop star gave birth in a New York hospital with her husband Jay Z, whose real name is Shawn Carter, by her side.

Celebrity friends took to Twitter to congratulate the couple on the birth although they themselves have not issued any official confirmation of the baby's arrival.

Hollywood actress Gwyneth Paltrow and her husband Coldplay frontman Chris Martin are close friends with the new parents and Paltrow tweeted to say the baby would be called Blue Ivy Carter.

The subject was a trending topic on the social networking site all day, but until Paltrow waded into the flurry of speculation on Twitter it was thought the child was to be called Ivy Blue.

Popstar Rihanna also offered her congratulations on Twitter.

"Welcome to the world princess Carter! Love Aunty Rih," the Telegraph quoted her as tweeting.

Beyonce announced her pregnancy at the 2011 MTV Video Music Awards in August, cradling her bump on the red carpet before unveiling it on stage during her performance by opening her sparkly blazer. (ANI)