Britain's Prince Philip, husband of Queen Elizabeth II, has died, Buckingham Palace said Friday. He was 99.

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

The prince "passed away peacefully" on Friday morning at Windsor Castle, according to the palace. He had recently spent a month in the hospital, returning to the castle on March 16.

File photo taken May 9, 1975, shows Britain's Queen Elizabeth II and Prince Philip waving to people in front of Tokyo's Hibiya Park. Prince Philip has died at the age of 99, Buckingham Palace said on April 9, 2021. (Kyodo) ==Kyodo

British Prime Minister Boris Johnson expressed his condolences in a statement, saying, "Prince Philip earned the affection of generations here in the United Kingdom, across the Commonwealth and around the world."

"Like the expert carriage driver that he was he helped to steer the royal family and the monarchy so that it remains an institution indisputably vital to the balance and happiness of our national life," Johnson said.

Born Prince Philip of Greece and Denmark, he married then Princess Elizabeth in 1947 and spent around 70 years supporting the queen before retiring from royal duties in 2017.

He was a patron of many organizations, including serving as the president of the World Wide Fund for Nature, and actively promoted causes in environmental protection, science and sports.

A naval commander during World War II, he had also spoken about being in Tokyo during Japan's surrender in 1945.

Prince Philip had close exchanges with the Japanese imperial family, with then Japanese Emperor Akihito and Empress Michiko visiting Britain as a state guest in 1998.

In 2001, he also met with Japanese Emperor Naruhito at Windsor Castle when he visited Britain as crown prince, and gave the Japanese royal a tour of a library in the castle.

Prince Philip also visited Japan several times, including as part of WWF activities.

Prince Charles, heir to the British throne, is the eldest of Prince Philip's four children with the queen.

File photo taken in May 2001 shows Britain's Queen Elizabeth II and Prince Philip explaining to Japanese Crown Prince Naruhito about items related to the Japanese imperial family at the Royal Library at Windsor Castle. Prince Philip has died at the age of 99, Buckingham Palace said on April 9, 2021. (Kyodo) ==Kyodo