Barack Obama has led tributes from around the globe to Baroness Thatcher, saying the "world has lost one of the great champions of freedom and liberty, and America has lost a true friend".

The US president joined world leaders past and present in paying tribute to the former prime minister.

He said in a statement: "As a grocer's daughter who rose to become Britain's first female prime minister, she stands as an example to our daughters that there is no glass ceiling that can't be shattered.

"As prime minister, she helped restore the confidence and pride that has always been the hallmark of Britain at its best.

"And as an unapologetic supporter of our transatlantic alliance, she knew that with strength and resolve we could win the Cold War and extend freedom's promise."

Mr Obama went on: "Here in America, many of us will never forget her standing shoulder to shoulder with President Reagan, reminding the world that we are not simply carried along by the currents of history - we can shape them with moral conviction, unyielding courage and iron will.

"Michelle and I send our thoughts to the Thatcher family and all the British people as we carry on the work to which she dedicated her life - free peoples standing together, determined to write our own destiny."

Mr Obama's predecessor, George W Bush, said that he and his wife, Laura, were saddened by Baroness Thatcher's death, it was reported.

In a statement he said: "She was an inspirational leader who stood on principle and guided her nation with confidence and clarity."

"Prime Minister Thatcher is a great example of strength and character, and a great ally who strengthened the special relationship between the United Kingdom and the United States.

"Laura and I join the people of Great Britain in remembering the life and leadership of this strong woman and friend."

Lech Walesa, the Polish anti-communist politician who led the Solidarity movement and was his country's first president after communism, hailed Baroness Thatcher as a "great person", it was reported.

He said: "She did a great deal for the world, along with Ronald Reagan, Pope John Paul II and Solidarity, she contributed to the demise of communism in Poland and Central Europe."

Another prominent figure in the fight against communism in Europe, Vaclav Klaus, said her name will always remain important.

In a statement on his website, the former Czech president, who entered politics during the country's Velvet Revolution, said her death "is for all supporters of freedom, democracy, market capitalism and a huge loss.

"She was one of the most prominent political figures last quarter of the 20th century, and I believe that the passage of time, her name will not lose its importance," he said.

South African's ruling African National Congress party expressed its sadness at Baroness Thatcher's death, despite being on the "receiving end" of her policies.

In a statement on their website, the party said: "The African National Congress has learnt with sadness of the passing of Mrs Margaret Thatcher, the former prime minister of Britain at the age of 87."

The statement went on: "The ANC was on the receiving end of her policy in terms of refusing to recognise the ANC as the representatives of South Africans and her failure to isolate Apartheid after it had been described as a crime against humanity, however we acknowledge that she was one of the strong leaders in Britain and Europe to an extent that some of her policies dominate discourse in the public service structures of the world.

"Long after her passing on, her impact will still be felt and her views a subject of discussion.

"The ANC extends its condolences to her family, her loved ones and the people of Britain. May her soul rest in peace."

Reformist Soviet leader Mikhail Gorbachev offered his "sincere condolences" to Baroness Thatcher's family and friends, describing the former prime minister as a "heavyweight politician".

"Thatcher was a politician whose word carried great weight," he reportedly said.

"Our first meeting in 1984 set in train relations that were sometimes complicated, not always smooth, but which were serious and responsible on both sides.

"Human relations also gradually took shape, becoming more and more friendly.

"In the end we managed to achieve a mutual understanding, and that contributed to a change in the atmosphere between our country and the West and the end of the Cold War.

"Margaret Thatcher was a heavyweight politician and a striking person. She will remain in our memories, and in history."

Current politicians around the world also commented on Baroness Thatcher's death.

German Chancellor Angela Merkel reportedly praised her actions in helping to bring about the end of the Cold War.

"As a long-serving prime minister, she shaped modern Britain as few have before or since," she said.

"She was one of the greatest leaders in world politics of her time.

"The freedom of the individual was at the centre of her beliefs so she recognised very early the power of the movements for freedom in Eastern Europe. And she supported them.

"I will never forget her contribution in overcoming Europe's partition and the end of the Cold War.

"Margaret Thatcher was not a feminist but by proving herself as a woman in the highest democratic post when this was far from usual, she gave an example to many. My thoughts and sympathy are with her children."

Canadian Prime Minister Stephen Harper called Baroness Thatcher "a giant among leaders".

In a statement, the Canadian Conservative leader said: "While many in positions of power are defined by the times in which they govern, Margaret Thatcher had that rarest of abilities to herself personify and define the age in which she served.

"Indeed, with the success of her economic policies, she defined contemporary conservatism itself.

"In 2006 I met with her in London, where she provided me wise and gracious counsel, the memory of which I will forever cherish. Laureen (Mr Harper's wife) and I join all Canadians in saluting the proud life and legacy of Lady Thatcher."

Israeli Prime Minister Benjamin Netanyahu said she was a "staunch friend of Israel and the Jewish people".

"Today I mourn the passing of prime minister Baroness Margaret Thatcher," he said.

"She was truly a great leader, a woman of principle, of determination, of conviction, of strength; a woman of greatness.

"She was a staunch friend of Israel and the Jewish people.

"She inspired a generation of political leaders.

"I send my most sincere condolences to her family and to the government and people of Great Britain."

French President Francois Hollande reportedly said Baroness Thatcher was a "great figure who left a profound mark on the history of her country".

He added: "Throughout her public life, with conservative beliefs she fully assumed, she was concerned with the United Kingdom's influence and the defence of its interests.

"She maintained a relationship with France that was frank and honest.

"Together they (Baroness Thatcher and former French president Francois Mitterrand) worked to strengthen the ties between our two countries.

"And it was at this time that Mrs Thatcher gave the decisive impetus to the construction of the cross-Channel Tunnel."