She said Yanukovich, the favourite to win the February 7 poll, was massing supporters around the capital Kiev and preparing to use "any means" to take power.
"The electoral commission acts like everything is fine, (but) in the polling stations there are falsifications," Tymoshenko said in the transcript of an interview with a Ukrainian television station made available on the government website.
"And around Kiev, all the holiday centres are full of fighters who are ready to take power using any means," the prime minister added.
"We remember all that from 2004. Yanukovich hasn't changed, his methods haven't changed, and his policies haven't changed," Tymoshenko is quoted as saying.
Mass rigging blamed on Yanukovich supporters and resulting protests which brought hundreds of thousands of Ukrainians onto the streets in the Orange Revolution forced the annullment of the 2004 presidential polls.
"As in 2004, we are going to put (Yanukovich) in his place in a severe manner and he will never get power in Ukraine, whatever the circumstances," said Tymoshenko, who was one of the leaders of the Orange Revolution.
Yanukovich led Tymoshenko by 10 percentage points in the first round.