Former New Zealand rugby star Jonah Lomu has died at the age of 40.

The All Blacks legend passed away unexpectedly in Auckland on Tuesday, reports TV3.

Lomu's death was confirmed by former All Blacks team doctor John Mayhew.

"On behalf of the Lomu family, I can confirm that Jonah Lomu died this morning, most probably about eight or nine," he said. "The family are obviously devastated, as are friends and acquaintances.

"The family have requested privacy at this stage, they are obviously going through a terrible time. It was totally unexpected. Jonah and his family arrived back from the United Kingdom last night and he suddenly died this morning."

The news was later acknowledged by New Zealand Rugby, which issued a tribute to the late sports star.

"We're all shocked and deeply saddened at the sudden death of Jonah Lomu," said the governing body's chief executive Steve Tew in a statement.

"Jonah was a legend of our game and loved by his many fans both here and around the world. We're lost for words and our heartfelt sympathies go out to Jonah's family."

Lomu had suffered from ill health since retiring from professional rugby in 2002 due to the rare kidney disease Nephrotic syndrome. He underwent a kidney transplant in 2004 and regular dialysis treatment since then.

Regarded as one of New Zealand's all-time greats, Lomu played in 63 Tests for his country since making his debut in 1994 and scored 43 tries at international level.