Britain mourns Princess Margaret

(CNN) -- Britain's Queen Elizabeth has declared a period of royal mourning for Princess Margaret, her younger sister, who died at age 71.

Princess Margaret died "peacefully in her sleep" at 6:30 a.m. Saturday (1:30 a.m. ET) after suffering a stroke, Buckingham Palace announced. Her children, Lord Linley, 40, and Lady Sarah Chatto, 37, were at her side.

The palace said Princess Margaret suffered a stroke Friday afternoon and developed cardiac problems during the night. She was taken to the hospital at 2:30 a.m. Saturday.

Her body was moved to Kensington Palace Saturday afternoon in a coffin draped with her personal standard and an arrangement of white lilies.

Margaret's mother "has been told of the sad news of the death of Princess Margaret and she is deeply saddened," according to a statement from the queen mother's official residence, Clarence House.

Prince Charles described Princess Margaret as his "darling aunt" and said it had been "a terribly sad day" for the royal family.

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"The last few years with her awful illness were hard for her to deal with, particularly as she was such a wonderfully vibrant woman with such a free spirit," he said.

Margaret was a heavy smoker for many years. She suffered repeated respiratory illnesses and had part of a lung removed in January 1985. She had a mild stroke in February 1998 and another in March 2001

Confined to a wheelchair and often donning heavy dark glasses, she was last seen in public before Christmas at the 100th birthday party for Princess Alice, the dowager duchess of Gloucester, widow of the third son of George V, the queen's grandfather.

A semi-private funeral service was scheduled Friday at St. George's Chapel, Windsor, 20 miles west of London. A public memorial service will also be held.

Until then, as part of the period of mourning, members of the royal family and their households will wear dark colors and black ties. Military officers on public duties will wear black armbands.

Official duties will continue for members of the royal family but social engagements have been postponed.

The flag at Buckingham Palace was lowered to half-staff and moments of silence were held at major sporting events.

Tributes poured in from around the world after her death was announced.

"She will be remembered with a lot of affection," said British Prime Minister Tony Blair during an official visit to Sierra Leone.

"Before she was ill the last few years, she gave a great deal of service to the country. And our thoughts are with the queen mother and all of the royal family at this difficult time," he said.

President Bush, who was in Jackson Hole, Wyoming, said that he and first lady Laura Bush were deeply saddened to learn of the princess' death.

"Princess Margaret was a proud mother and grandmother whose compassion and support for charities helped better the lives of many in need," Bush said in a statement. "Our thoughts and prayers are with her children, grandchildren and the entire royal family."

Princess Margaret, the younger daughter of King George VI and Queen Elizabeth, the queen mother, was born August 21, 1930, in Scotland.

The British flag flies at half-staff Saturday over Windsor Castle.

In the 1950s, she had a famous love affair with Royal Air Force Group Capt. Peter Townsend, a doomed romance that gripped the nation.

Townsend, also a royal equerry, or attendant, was divorced and the Church of England insisted that members of the royal family should uphold the church's teachings on the sanctity of marriage.

Her decision to renounce Townsend for the sake of the monarchy won the nation's sympathy. Townsend died in 1995.

On May 6, 1960, the princess married society photographer Antony Armstrong-Jones in Westminster Abbey. In October of that year, Armstrong-Jones was created Earl of Snowdon and Viscount Linley.

The couple had two children before divorcing in May 1978.

Snowdon said he and the children were "extremely saddened."

Many of Britain's older generation remember Princess Margaret as the "party princess." In the 1960s and 1970s, Margaret became somewhat of a jet-setter, attending high-profile parties and becoming a heavy smoker and drinker.

Princess Margaret's death comes amid her sister's Golden Jubilee, the 50th anniversary of her accession to Britain's throne.

Although considered a somber commemoration because it marks the death of the king 50 years ago, a jubilee often is celebrated with street parties and well-wishers.

As part of the jubilee, the queen had planned to begin a trip to Jamaica, New Zealand and Australia February 18. The palace said it was too early to say whether she would cancel the trip.