The Nobel Peace laureate has in recent years appeared tired during public appearances.
He is diabetic, according to media reports.
Gorbachev became Soviet leader in 1985 and instituted the sweeping political and economic reforms that became known as glasnost ("openness") and "perestroika" (rebuilding).
In 1991 his reforms gave the Moscow-controlled republics enough strength to declare independence, and for Russia together with Belarus and Ukraine to sign an agreement on the Soviet Union's dissolution.
He has since lamented the Soviet Union's collapse, explaining that his reforms were meant to save the crumbling country through modernisation instead of breaking it apart.
Despite his broad global recognition, in recent years Gorbachev has played only a marginal role in Russian politics, though he has criticised Russian President Vladimir Putin and called for him to give up power.
He presides over the Gorbachev Foundation for research and charitable programs.
- AAP
