MOSCOW, August 4 (RIA Novosti) - A ceremony to pay tribute to Russian writer Alexander Solzhenitsyn will take place at the Academy of Sciences on Tuesday, the Solzhenitsyn foundation has said.

"The ceremony will begin at 11:00 Moscow time (7:00 GMT) and will most likely last through the day," the foundation said.

Solzhenitsyn died of heart failure in Moscow late on Sunday at the age of 89.

Russian President Dmitry Medvedev and Prime Minister Vladimir Putin expressed their condolences to the writer's widow and his three sons. Other world leaders, including French President Nicolas Sarkozy and U.S. President George W. Bush, also paid tribute to the man who did much to tell the world about the horrors of the Soviet system of labor camps, or the Gulag.

In a telegram from the Russian government to his family, Solzhenitsyn was called "the country's conscience and an embodiment of internal freedom and dignity," and "a man, whose books and life served as moral guidelines for the nation."

Best known for The Gulag Archipelago, Solzhenitsyn fought in WWII, endured eight years in labor camps and survived cancer in the absence of almost any medication.

He first came to acclaim in Russia and the world during Soviet leader Nikita Khrushchev's political "thaw," when his One Day in the Life of Ivan Denisovich - an account of gulag life - was published in 1962 in the Soviet literary journal Novy Mir.

One Day in the Life of Ivan Denisovich is the story of a labor camp inmate who almost forgets his name, remembering only his prisoner number. The man gets so used to prison horrors and perpetual humiliation that he regards them as normal life. The book caused a sensation in the Soviet Union and abroad and made Solzhenitsyn famous overnight.

The thaw eventually ended however, and Solzhenitsyn again fell out of favor with the authorities under new Soviet leader Leonid Brezhnev. His works were seized, and the distribution of home-printed copies, or samizdat, of his stories became a criminal offense.

In 1970, he was awarded the Nobel Prize in Literature, further outraging the Soviet authorities.

Solzhenitsyn was stripped of his Soviet citizenship and exiled to West Germany in 1974. He soon moved to the United States, where he spent the next 20 years working on his historical cycle of the Russian 1917 revolution, while also publishing several shorter works.

He returned to Russia in 1994, three years after the collapse of the U.S.S.R.

"The world has lost one of the symbols of freedom," former French President Jacques Chirac said, as quoted by the AFP agency. "Russia has lost a great fighter for the truth, who worked to reconcile Russians with their past."

Solzhenitsyn will be buried at the Donskoy Monastery in Moscow on Wednesday, according to a church official.