Mikhail Gorbachev, the former Soviet leader who brought the Cold War to a peaceful end, has died aged 91.

Mr Gorbachev, who took power in 1985, opened up the Soviet Union to the world and introduced a set of reforms at home.

But he was unable to prevent the slow collapse of the Soviet Union, from which modern Russia emerged.

Tributes have been paid worldwide, with UN chief António Guterres saying he "changed the course of history".

"Mikhail Gorbachev was a one-of-a kind statesman," UN Secretary General Mr Guterres wrote in a Twitter tribute. "The world has lost a towering global leader, committed multilateralist, and tireless advocate for peace."

The hospital in Moscow where he died said he had been suffering from a long and serious illness.

In recent years his health has been in decline and he had been in and out of hospital. In June, international media reported that he had been admitted after suffering from a kidney ailment, though his cause of death has not been announced.

Russian President Vladimir Putin has expressed his deepest condolences following Mr Gorbachev's death, his spokesman Dmitry Peskov said.

US President Joe Biden called him a "rare leader" and praised Mr Gorbachev as a unique politician who had the "imagination to see that a different future was possible" amid the tensions of the Cold War.