On Sunday, Russian TV presenter and former presidential candidate Ksenia Sobchak said that Chubais had been admitted to a European clinic in a moderately severe state with the Guillain-Barre syndrome.
The 67-year-old politician was hospitalized in the city of Olbia and is in serious condition at the moment, Italian newspaper Corriere della Sera reported.
The John Paul II hospital, one of the biggest medical institutions in Olbia, declined to comment on Chubais' condition and hospitalization when asked by Sputnik.
The Guillain-Barre syndrome is a rare neurological disorder caused by the immune system attacking nerves. It can have various causes, including bacterial and viral infections, and is most common in males and people over 50.