Mikhail Gorbachev, the last leader of the Soviet Union, has died at the age of 91.
Mr Gorbachev's office earlier said that he was undergoing treatment at the Central Clinical Hospital in Moscow.
He died after a long illness, the hospital was quoted as saying by news agencies.
Perhaps Moscow’s most revolutionary leader since Stalin, Mr Gorbachev took power in 1985 and began systematically dismantling the Iron Curtain that ran through the heart of Europe.
Famously, he got on well with western leaders; he agreed with Ronald Reagan to reduce the Soviet Union’s stock of medium-range nuclear missiles and in 1988 withdrew Moscow’s troops from Afghanistan.
Even former British Prime Minister Margaret Thatcher - no friend of the Kremlin - declared herself a fan. “I like Mr Gorbachev,” she said. “We can do business together.”
1989 was the year the Berlin Wall fell and quickly afterwards the nations of Eastern Europe began to declare themselves independent of Moscow.
For many Russians, it was a bitter pill that they have never gotten over.
In August 1991, Gorbachev was on holiday in Crimea when Soviet hardliners launched a coup d’état.
While the revolution lasted a mere three days, it ultimately did not stop Ukraine declaring independence that same month.
Mr Gorbachev spent his last months in office watching republic after republic declare independence until he resigned on Christmas Day the same year.
The following day, the Soviet Union was formally dissolved.
Taoiseach Micheál Martin said he was "saddened" to hear of his passing.
"His sense of history, and commitment to openness, reform, and building bridges with the West, changed the world", he wrote on Twitter.
Saddened to hear of the passing of Mikhail Gorbachev.
His sense of history, and commitment to openness, reform, and building bridges with the West, changed the world.
— Micheál Martin (@MichealMartinTD) August 30, 2022
US President Joe Biden praised Mr Gorbachev's achievements in believing "in a better world" and dramatically reducing the potential for a third world war.
"As leader of the USSR, he worked with President Reagan to reduce our two countries' nuclear arsenals, to the relief of people worldwide praying for an end to the nuclear arms race," said Mr Biden in a statement.
"These were the acts of a rare leader.
"One with the imagination to see that a different future was possible and the courage to risk his entire career to achieve it. The result was a safer world and greater freedom for millions of people," Mr Biden added.
Russian President, Vladimir Putin, has expressed his deepest sympathy, a spokesman for the Kremlin said.
Additional reporting: Jack Quann/IRN
Main Image: Gorbachev Picture by: Alamy.com