Tymoshenko, a hugely controversial figure both in Ukraine and Russia who was released from jail last month, confirmed the voice was hers but said some of the comments had been manipulated.
"This really crosses all the boundaries," Tymoshenko is heard to say in the leaked phone call posted on YouTube and broadcast extensively on Russian television yesterday.
"One has to take up arms and go wipe out these damn 'katsaps' together with their leader," the voice said in Russian, without mentioning Putin by name.
During the conversation, Tymoshenko is said to discuss Russia's seizure of Ukraine's Russian-speaking peninsula of Crimea with Ukrainian MP and former government official Nestor Shufrych.
More From This Section
Tymoshenko, who spent three years in jail on what her supporters say were politically motivated charges of abuse of power before being freed last month, said if she were in power Moscow would not be able to take the peninsula.
"I am sorry that I am not able to be there and am not in charge of these processes, they wouldn't have had a fucking chance of getting Crimea off me."
"I am hoping that I will use all my connections and will get the whole world to rise up so that not even scorched earth would be left of Russia."
Discussing the fate of Ukraine's eight million ethnic Russians with Shufrych, Tymoshenko was also heard as saying that they should be "nuked".