Britain's Prince Philip, Duke of Edinburgh and husband of Queen Elizabeth II, has died aged 99, Buckingham Palace said on Friday.

"It is with deep sorrow that Her Majesty The Queen announces the death of her beloved husband, His Royal Highness Prince Philip, Duke of Edinburgh," the palace said in a statement.

"His Royal Highness passed away peacefully this morning at Windsor Castle. Further announcements will be made in due course. The Royal Family join with people around the world in mourning his loss."

Prince Philip will not have a state funeral nor lie in state for the public to pay their respects ahead of the funeral, the College of Arms said, with arrangements revised to meet COVID-19 restrictions.

"The funeral will not be a State Funeral and will not be preceded by a Lying-in-State. His Royal Highness's body will lie at rest in Windsor Castle ahead of the funeral in St George's Chapel. This is in line with custom and with His Royal Highness's wishes," the College of Arms said on Friday.

The Duke of Edinburgh left hospital last month after a month-long treatment. He underwent a procedure for a pre-existing heart condition, according to Buckingham Palace.

Prince Philip had been by his wife's side throughout her 69-year reign, the longest in British history.

A Greek prince, he married Elizabeth in 1947, playing a key role in modernizing the monarchy in the post-World War II period, and behind the walls of Buckingham Palace being the one key figure the Queen could turn to and trust. 

"He has, quite simply, been my strength and stay all these years," Elizabeth said in a rare personal tribute to Philip made in a speech marking their 50th wedding anniversary in 1997. 

"I, and his whole family, and this and many other countries, owe him a debt greater than he would ever claim, or we shall ever know."

The couple had four children: Charles, Prince of Wales (born in 1948), Princess Anne (1950), Prince Andrew (1960) and Prince Edward (1964), three of whose marriages ended in divorce.

UK PM Johnson pays tribute to Prince Philip

British Prime Minister Boris Johnson paid tribute to Prince Philip after his death, saying the country would mourn with the royal family and Queen Elizabeth, who had lost her "strength and stay of more than 70 years". 

"We remember the duke ... above all for his steadfast support for Her Majesty the Queen, not just as her consort, by her side, every day of her reign, but as her husband, her strength and stay of more than 70 years," Johnson said. 

"And it is to Her Majesty, and her family, that our nation's thoughts must turn today."

(With input from Reuters)