Britain's Prince William and Duchess Catherine ''could not be happier'' following the birth of their son.

The Duke of Cambridge has made his first comments after his wife gave birth to their first child at 16:24pm BST on Monday (22.07.13), and he says the couple are ecstatic to welcome the newborn.

In a short statement, he said: ''We could not be happier.''

The new royal heir - who will be third in line to the throne after his father and grandfather Prince Charles - weighed 8lbs, 6oz, and was born in the late afternoon in the Lindo Wing at St. Mary's Hospital in Paddington, London.

The Prince of Cambridge and his mother are both doing well and are expected to remain in hospital overnight.

Prince William informed his father, grandmother Queen Elizabeth and brother Prince Harry of his son's birth shortly before an official announcement was made to the public via press release.

Congratulations have poured in for the royal couple and the new prince from all around the world.

British prime minister David Cameron said: ''It is wonderful news from St. Mary's, Paddington, and I am sure that right across the country, and indeed right across the Commonwealth, people will be celebrating and wishing the royal couple well.

''It is an important moment in the life of our nation but, I suppose, above all it is a wonderful moment for a warm and loving couple who have got a brand new baby boy.''

Meanwhile, the United States president Barack Obama also released a statement on behalf of himself and wife Michelle Obama.

He said: ''Michelle and I are so pleased to congratulate The Duke and Duchess of Cambridge on the joyous occasion of the birth of their first child. We wish them all the happiness and blessings parenthood brings.''