MOSCOW - Natalia Bessmertnova, a Soviet-era prima ballerina who danced with the Bolshoi Ballet for decades, died Tuesday, a spokeswoman for the ballet said. She was 66.

Bessmertnova died at a Moscow hospital after suffering from a grave illness, Yekaterina Novikova said, but she would not specify the cause of death. Russian media reported that Bessmertnova had kidney trouble.

Bessmertnova was a top dancer at the Bolshoi from 1961 until 1995, the year she and other performers staged a one-night strike after the ballet's longtime artistic director Yuri Grigorovich, her husband, quit during a dispute with management amid plans for his replacement.

Their refusal to perform "Romeo and Juliet" prompted the first cancellation in the ballet's more than two-century-long history.

In addition to Juliet, Bessmertnova also danced the leading female roles "Giselle," "Ivan the Terrible," "The Angara" and "The Golden Age."

Bolshoi director Anatoly Iksanov called Bessmertnova's death "a huge loss for the Bolshoi Theater and to our whole culture," the ITAR-Tass news agency said.

The dancer was "the pride and glory of the company to which she devoted her entire life," he was quoted as saying.

Bessmertnova was born in Moscow to a doctor and a homemaker. She showed an early interest in dance and soon displayed talent to match, joining the Bolshoi immediately after graduating from the theater's developmental school.

She was named a People's Artist of the U.S.S.R. in 1976 and was a laureate of the Soviet Union's Lenin Prize and State Prize.

She was a gold medalist at the prestigious Varna International Ballet Competition in 1965 and was awarded France's Pavlova Prize in 1970.

In recent years, Bessmertnova had worked with Grigorovich on projects such as the Benois de la Danse Prize, for which he served as chairman of the jury.

Funeral plans were not immediately available.