Dr Manmohan Singh tweeted: "I express my deepest sadness on the passing away of former British Prime Minister Baroness Margaret Thatcher.
"She was a transformative figure under whom the United Kingdom registered important progress on the national and international arena.
"People of India join me in sending our sincerest condolences to the Thatcher family, the Government and people of the United Kingdom."
British Prime Minister, David Cameron tweeted on his official account, "It was with great sadness that l learned of Lady Thatcher’s death. We've lost a great leader, a great Prime Minister and a great Briton"
"It was with great sadness that l learned of Lady Thatcher’s death. We've lost a great leader, a great Prime Minister and a great Briton,” said London Mayor, Boris Johnson.
Spice girl Geri Halliwell tweeted, "Thinking of our 1st Lady of girl power, Margaret Thatcher, a green grocer's daughter who taught me any thing is possible...x"
US senator and former presidential candidate John McCain wrote: "RIP Margaret Thatcher, one of the great leaders of the 20th century."
'Ae Dil Hai Mushkil': Ranbir, Aishwarya, Anushka on 'The Kapil Sharma Show'
Photos: Huma Qureshi, Neha Dhupia and other celebs at MAMI
Flashback: When sexy models sizzled in bikinis at Tokyo fashion show
Photos: Amy Jackson, Daisy Shah at Mumbai airport
Photos: Sridevi, Irrfan and other celebs at 'Mughal-e-Azam' screening