'LONDON, United Kingdom (AFP) - British Prime Minister David Cameron on Thursday said "a great light had gone out" following Mr Nelson Mandela's death, revealing that flags would be flown at half-mast at his Downing Street Office.

"A great light has gone out in the world," Mr Cameron wrote on his official Twitter account.

"Nelson Mandela was a hero of our time. I've asked for the flag at No.10 to be flown at half mast."

A Downing Street spokesman said a fuller statement was expected later.

Shadow finance minister Ed Balls also took to Twitter, writing: "Seeing Nelson Mandela walking free is one of the great moments of my life - proving leadership and hope can triumph. Thank-you. RIP"

Irish prime minister Enda Kenny paid tribute to the "gift" of Mr Mandela, and offered the country's deepest sympathies to the people of South Africa.

"The name Mandela stirred our conscience and our hearts. It became synonymous with the pursuit of dignity and freedom across the globe," he said in a statement.

"As we mark his passing, we give thanks for the gift of Nelson Mandela. We ask that his spirit continues to inspire, guide and enlighten us as we strive to bring freedom and dignity to the family of man, our brothers and sisters, across the world," he added.