Russian President Vladimir Putin will put off his annual state-of-the nation address to parliament until Thursday due to the sudden death of former president Boris Yeltsin, the Kremlin press service said on Tuesday.

Putin will address parliament at 12:00 Moscow time (0800 GMT) in the Marble Hall of the Kremlin, it said.

Russia's first president Yeltsin, aged 76, died of heart failure on Monday in a Kremlin hospital in Moscow.

Putin declared April 25 a day of national mourning for the late former president, who will lie in state at Moscow's Christ the Saviour Cathedral for people to pay their last tribute and will be buried at Moscow's historic Novodevichye cemetery on that day.

"A new era began thanks to Boris Nikolayevich -- a free and democratic Russia with a new constitution that gave people an opportunity to express their thoughts freely," Putin said in a special televised address on Tuesday.

Some foreign leaders, as well as Russian senior officials and lawmakers have expressed their condolencess.

Yeltsin is survived by his wife, Naina, 75, as well as two daughters, five grandchildren and three great-grandchildren.

Source: Xinhua