Vasily Aleksanyan said, "From today I am on hunger strike, and will only drink water until my release."
Aleksanyan was arrested Thursday after a Moscow court ruled that prosecutors could charge him with embezzling $460 million and money laundering, his defense lawyer, Gevorg Davgyan, said.
Aleksanyan denied any wrongdoing ahead of that ruling.
"As you can see, I am staying in Russia, am not trying to flee the country, and I do not believe I am guilty of anything," said Aleksanyan, who as head of the Yukos legal department acted for ex-Yukos CEO Mikhail Khodorkovsky and former Yukos-Moscow president Vasily Shakhnovsky at their trials.
Prosecutors accuse Aleksanyan of embezzling $460 million from Yukos production unit Tomskneft, and the funds of some other oil companies, and of laundering another $460.8 million through his personal account in a Swiss bank.
"Aleksanyan is a well-educated man, and has long been a member of an organized group, and did not commit such felonies by accident," Prosecutor Valery Lakhtin said, adding that Aleksanyan, if found guilty, would face between 10 and 15 years in jail.
Aleksanyan said the decision to charge him could be linked to his appointment as Yukos executive vice president, a move the Yukos board endorsed Tuesday.
The board said Aleksanyan would be entrusted with representing the interests of stakeholders, including creditors and shareholders, and ensuring that the company's assets were protected.
