Barbara Bush, the wife of former US President George H.W. Bush, died on Tuesday at the age of 92, a family spokesman said without elaborating.

Spokesman Jim McGrath announced on Sunday that Barbara, who had been suffering from poor health, had been placed in palliative care.

She had received medical treatment for chronic obstructive pulmonary disease and congestive heart failure, according to media reports, and had suffered for decades from a thyroid condition known as Graves' disease.

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'Mom kept us on our toes'

Following news of her death, tributes to Bush poured in from world leaders, US politicians, and her children.

Her son, former US President George W. Bush, said in a statement: "Mom kept us on our toes and kept us laughing until the end. I'm a lucky man that Barbara Bush was my mother."

Current US President Donald Trump said that the late Bush will be remembered "for her strong devotion to country and family, both of which she served unfailingly well."

On Twitter, former US President Bill Clinton praised Bush's "grit & grace, brains & beauty" and said he and his wife, former Secretary of State Hillary Clinton, "mourn her passing and bless her memory."

Former President Barack Obama and his wife Michelle said in a statement: "We'll always be grateful to Mrs. Bush for the generosity she showed to us throughout our time in the White House, but we're even more grateful for the way she lived her life — as a testament to the fact that public service is an important and noble calling."

Canadian President Justin Trudeau sent his condolences, writing on Twitter: "Always a friend to Canada, Barbara Bush leaves a legacy of dignity, grace, service and devotion to family."

Literacy promoter

During her husband's time in office, Barbara was known for her down-to-earth demeanor and putting herself largely above the political fray.

She promoted children's literacy, founding the Barbara Bush Foundation for Family Literacy, and is said to have convinced her husband to boost funding for AIDS research and treatment.

Barbara was only the second woman after Abigail Adams, who was the wife of John Adams and mother of John Quincy Adams, to have been both a first lady and the mother of a US president.

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rs, amp/aw (AP, dpa, Reuters)