“As Anna Akhmatova, the great poetic chronicler of Stalin’s terror, said, ‘I am alive in this grave,’ ” Ms. Tymoshenko wrote in an essay published in The Moscow Times. “Indeed, I am more alive than the men who have imprisoned me here.”

The Ukrainian authorities took pains on Friday to suggest that Ms. Tymoshenko was being held in comfortable conditions. The State Penitentiary Service rebutted reports that she had been taken to the prison in a wheelchair, saying she was moved in “a comfortable minibus with all the accommodations (biotoilet, wash basin, two couches.)” It also said that Ms. Tymoshenko had 12 suitcases for her personal effects that required the use of a second vehicle.

Her supporters said the move was sudden and traumatic, and promised to drive immediately to the village where the prison camp is situated. Oleksandr Turchynov, the deputy chief of her Batkivshchyna Party, told reporters that Ms. Tymoshenko’s mother arrived at 6 a.m. Friday at the jail where her daughter had been held only to be told that “no such prisoner is in this detention center.”

“Tymoshenko was taken at night, without any warning or explanation, and early in the morning, actually on a stretcher, she was loaded onto a truck and driven in the direction of Kharkiv,” a city near the new prison, Mr. Turchynov said, in comments carried by the Interfax news service. He said the transfer was “a New Year’s present for President Yanukovich,” who he said was annoyed by her writings from prison.

Last week, an appeals court in Kiev upheld the ruling against Ms. Tymoshenko, which centered on the gas deal with Russia, in 2009. She boycotted the appeals hearings, saying in a statement that “seeking truth and justice in the Ukrainian courts is completely futile.”