A veteran Russian musician and music producer, Bari Alibasov, has reportedly been hospitalized with symptoms of poisoning and his condition is described as grave.
Alibasov was hospitalized a day earlier with burns to his stomach and digestive system, Russian media quoted Moscow's Sklifosovsky Medical Center as saying on June 5.
Alibasov's spokesman, Sergei Motsar, said earlier that Alibasov had mistakenly drunk from a glass containing toxic chemicals while at home.
Alibasov, 71, was born in Kazakhstan's northeast. In the late 1960s, he formed the jazz-rock group Integral in the city of Oskemen in East Kazakhstan at a time when rock was frowned upon by Soviet authorities.
The group later came to prominence across the former Soviet Union until it disbanded in 1989.
In the early 1990s, Alibasov's new project -- a pop band called Na-Na -- became very popular in Russia and many other former Soviet republics.