Former Soviet Union (USSR) President Mikhail Gorbachev died at 91 years old, the Moscow Central Clinical Hospital said on Tuesday.

"Mikhail Sergeevich Gorbachev died this evening after a serious and long illness," the hospital told reporters. 

Gorbachev served as the last president of the Soviet Union. His policies are blamed by many to have been one of the chief catalyzers for the fall of the USSR. 

He sought to consolidate ties with the West and forged arms reduction treaties with the United States, as well as agreements with Western powers, which led to the incorporation of the Democratic People's Republic of Germany into West Germany.

He was highly lenient toward capitalism and the privatization of various sectors of the Soviet Union, and due to his failure to keep the USSR together, one by one, the Soviet Republics were ceded from the union until its collapse on December 26, 1991.

Following the fall of the USSR, Gorbachev appeared controversially in a Pizza Hut commercial, which to this day, is viewed negatively by most of the Russian public.

He became Secretary-General of the Soviet Communist Party in 1985 at 54. Gorbachev wanted to embark on a path of liberalization, introducing limited political and economic freedoms until his reforms, which were under the title of Perestroika [reconstruction], went out of control.

Many Russians never forgave Gorbachev for the turbulence and crises caused by his heavily criticized reforms, taking into consideration the subsequent decline in their living standards was too expensive a price to pay for the "democracy" pushed by the West.

Gorbachev headed the USSR since he came to power in 1985 until the fall of the union at the end of 1991.