In a condolence telegram sent on Wednesday, Russian President Vladimir Putin said Gorbachev had a "huge impact on the course of world history."

Putin said the USSR's last leader "deeply understood that reforms were necessary" and strove to offer his own solutions to the problems it faced in the 1980s.

Former German Chancellor Angela Merkel, who grew up in communist-controlled East Germany, said Gorbachev had completely changed her life and the world.

"He showed by example how a single statesman can change the world for the better," she wrote in a statement. "Gorbachev also changed my life in fundamental ways. I will never forget it."

Her successor Olaf Scholz hailed Gorbachev's role in reuniting Germany on Wednesday, but pitied that his attempt to establish a lasting democracy in Russia had "failed."

"The democracy movements in central and eastern Europe benefited from the fact he was in power," Scholz said. Yet Gorbachev "died at a time in which democracy has failed in Russia."

Lithuania's Foreign Minister Gabrielius Landsbergis said his compatriots would never "glorify" Gorbachev.

"We will never forget the simple fact that his army murdered civilians to prolong his regime's occupation of our country, " he wrote on Twitter Wednesday morning. "His soldiers fired on our unarmed protestors and crushed them under his tanks."

"That is how we will remember him."

Ursula von der Leyen, the president of the European Commission, said his legacy would not be forgotten.

“Mikhail Gorbachev was a trusted and respected leader," she said. "He played a crucial role to end the Cold War and bring down the Iron Curtain. It opened the way for a free Europe ... R.I.P Mikhail Gorbachev.”

French President Emmanuel Macron described the 91-year-old as a “man of peace”.

He said Gorbachev had “opened a path of liberty for Russians. His commitment to peace in Europe changed our shared history.”

Boris Johnson, the outgoing UK prime minister, said he “always admired the courage and integrity he [Gorbachev] showed in bringing the Cold War to a peaceful conclusion”.

"In a time of Putin’s aggression in Ukraine, his tireless commitment to opening up Soviet society remains an example to us all," Johnson added.

Reactions to Gorbachev's passing in Ukraine are more divided.

Some commentators said he mishandled the Chornobyl nuclear disaster, which killed thousands, while others recognized how he paved the way for Ukrainian independence.

In Russia, the official reaction to the death of Gorbachev was more frosty, with the last Soviet leader viewed by some as the author of the USSR's demise.

A report by Russia's state-owned Tass news agency described Gorbachev in a dry, laconic way.

Their report simply stated that he had died and that Gorbachev "promoted ... political and economic reforms. He was the first and the last president of the Soviet Union, winning elections for the post in March 1990 and resigning on Dec. 25, 1991."

Others in Russia were more scathing.

Vitaly Milonov, a Russian MP, said the former Soviet president left a legacy “worse than Hitler for our country”, according to a tweet reported in the pro-Kremlin Federal news agency.

Milonov pointed out that it was telling that Gorbachev died amid a “deconstruction of the world order”, referring to the invasion of Ukraine, which is seen by some experts as an attempt by Putin to restore part of the USSR and revive the glory of the old superpower.

Lyubov Sobol, an ally of jailed Putin opponent Alexei Navalny, said there were "really different assessments of Gorbachev in his home country.

"Some write that he gave hope, others curse him for the collapse of the Soviet Union," he wrote. "The Soviet Union would have collapsed anyway. And the role of Gorbachev in history in Russia will still be appreciated."

In Eastern Europe, which gained independence under Gorbachev without bloodshed, the political legacy of the Soviet leader was applauded.

"He increased the scope of freedom of the enslaved peoples of the Soviet Union in an unprecedented way, giving them hope for a more dignified life," said Polish Foreign Minister Zbigniew Rau.

Anne Applebaum, a historian of Eastern Europe, said: “Not many people have it in their power to change the world as much as Mikhail Gorbachev did. Even if he didn’t start out wanting to do so.”

Outside of Europe, politicians in the US — the USSR's age-old foe — heaped praise on Gorbachev, who helped forge more peaceful relations between the Western and Eastern worlds.

US President Joe Biden called him a "rare leader", highlighting his work toward controlling arms.

“Mikhail Gorbachev was a man of remarkable vision," Biden said. "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."

“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," he added.

Now deceased, former US President Ronald Reagan was Gorbachev's main adversary in the West. But the pair ended up forming a good bond, which aided the end of the Cold War.

The Reagan Foundation and Institute said it mourned the death of a man “who once was a political adversary of Ronald Reagan’s who ended up becoming a friend."

"Our thoughts and prayers go out to the Gorbachev family and the people of Russia," it added.