Mrs Gorbachev, 67, died after losing a battle against leukaemia.

The BBC's Bridget Kendall reports: "Throughout her life, she and her husband were inseparable"

She had been receiving treatment in a clinic in the German city of Münster since 25 July, and had undergone chemotherapy.

"I send my heartfelt condolences, commending Raisa Maximovna Gorbacheva to almighty God's eternal love," the Pope said in a telegram.

"I hope that you will find in the affection of your family and friends the strength to endure this loss," he added.

Raisa Gorbachev accompanied her husband to a historic meeting with the head of world's Roman Catholics on 1 December 1989.

Yeltsin expresses sympathy

Only weeks ago Mr Gorbachev's sister Ludmilla Titorenko had flown to Münster after being identified as a suitable donor for a bone-marrow transplant.

Baroness Thatcher: Described Mrs Gorbachev as "articulate and charming"

Mikhail Gorbachev and the couple's daughter Irina had been staying in the city during the treatment.

A spokesman for the Gorbachev Foundation in Moscow said that the former president had been at his wife's bedside when she died.

Russia's President Boris Yeltsin led the messages of sympathy, saying that many people would be sharing Mr Gorbachev's pain.

"You lost a wonderful person, a beautiful woman, a loving wife and mother," he wrote to Mr Gorbachev; "today millions of Russians and people from other countries who knew and respected your spouse share your bitterness."

The president is sending a plane to Germany to return Mrs Gorbachev's body for a funeral and expected burial in Moscow, Russia's Itar-Tass news agency reported.

Post-Communist icon

A former philosophy teacher, Raisa Gorbachev was widely feted in the west as a symbol of change in the Soviet Union as she brought First Lady-style glamour into the Kremlin.

Mr Gorbachev was with his wife when she died

Following the nuclear disaster at Chernobyl in April 1986, she worked hard on behalf of children who had been contaminated during the accident.

Despite facing some hostility at home, the Gorbachevs remained very popular in Germany, where many see the former Soviet leader's 'perestroika' (restructuring) policies as leading to the fall of the Berlin Wall in 1989 and subsequent unification of the country.

Mr Gorbachev repeatedly blamed his wife's ill health on the "suffering" and "stress" caused by the failed coup attempt in August 1991, when Communist hardliners tried to remove him from power.

The couple were detained for three days in their official holiday retreat in Foros, on the Crimean coast.

Shortly afterwards Mrs Gorbachev suffered a stroke and spent 18 days in hospital.

Tributes

Former British prime minister Baroness Thatcher, who famously said that Mikhail Gorbachev was a man she could "do business with", was among the first to pay tribute.

Former Foreign Secretary Sir Malcolm Rifkind remembers Raisa Gorbachev.

"Raisa Gorbachev was a highly educated, articulate and charming woman," she said.

"She and her husband were an inseparable and devoted couple and Raisa's constant personal support made an enormous contribution to President Gorbachev's career and to the great reforms he brought about in the former Soviet Union."

Adding his voice to the tributes, Germany's Chancellor Gerhard Schröder wrote: "By your side, your wife embodied the breakthrough into a new world. We will never forget her."

And in France, President Jacques Chirac said: "At such a painful time, words are really powerless."