"Mstislav Leopoldovich feels better now. He is currently in a health rehabilitation center at Barvikha [a posh suburb west of Moscow]," a spokesperson for the Rostropovich Foundation said, without specifying why the musician had been hospitalized.
A family friend was quoted by media Thursday as saying that Rostropovich, 80, had been hospitalized, but did not specify when the hospitalization took place.
The musician spent several months in the hospital earlier this year, after he felt unwell during a December tour to Voronezh, in southern Russia.
He was discharged at the beginning of March, but looked frail at a Kremlin reception to celebrate his 80th birthday later that month, leading some media to speculate that he was being treated for cancer.
Dignitaries from around the world gathered in Moscow March 27 to honor the world-famous musician, who had been forced into exile and deprived of his Soviet citizenship in the 1970s for supporting Soviet dissident writer Alexander Solzhenitsyn and criticizing the lack of artistic and intellectual freedom in his country.
Since having his Russian citizenship restored in 1994, he has divided his time between homes in Russia, Western Europe and the United States.