Russia's first President Boris Yeltsin has died at the age of 76, a Kremlin spokesmen said Monday.

President Vladimir Putin has telephoned the widow Naina Yeltsin to offer sympathies.

The former president "died a sudden death in Moscow on Monday," the Itar-Tass news agency quoted Kremlin source as saying.

"Today, April 23, at 15:45 Moscow time, Russia's first President Boris Nikolayevich Yeltsin died at the Central Clinical Hospital. The death was caused by the progressing cardiovascular polyorganic insufficiency," Itar-Tass quoted head of the presidential administration's medical center Sergei Mironov as saying.

The White House mourned Yeltsin as "a historic figure" and offered condolences to his relatives, according to reports reaching here.

Former Soviet President Mikhail Gorbachev, also Yeltsin's once main opponent, has sent condolences to Naina, according to Itar- Tass.

"I addressed Naina and the whole family. I feel sincerely sorry for you and share your grief," Gorbachev was quoted as saying. " Life itself made out paths cross and we had to act at a time when dramatic changes were taking place in the country."

"There were many things where we disagreed and there were big disagreements, and this affected political processes, but at this moment I express my deep sympathy for the Yeltsin family," Gorbachev was quoted as saying.

Born on Feb. 1, 1931, Yeltsin worked as construction worker, communist party official and served as Russia's first democratically elected president since 1991. He led to the collapse of the Soviet Union.

He won a second term in an election in 1996 but transferred power to Putin and resigned from the post on Dec. 31, 1999. He then kept a low profile.

Yeltsin graduated in 1955 from the Urals Polytechnical Institute in Sverdlovsk (now Yekaterinburg), where he was born. He joined the Communist Party in 1961.

He became the first secretary of the Party's Sverdlovsk district central committee in 1976 and a member of the Party's central committee in 1981.

In 1985, he was pointed as chief the Party's Moscow branch and in 1986, an alternative member of the Party's top decision making body, the Politburo of the central committee.

He was forced to resign from the party leadership in 1988 after challenging Communist hard-liners and criticized Gorbachev's reforms. He was appointed as a deputy chairman of a construction committee.

Yeltsin resigned from the Communist Party in 1990 and became Russia's first democratically elected president in the popular election in 1991.

Source: Xinhua