Rosneft chief Sergei Bogdanchikov snubbed a court on Thursday by failing to respond to a subpoena as a defense witness in the politically tinged case of fallen oil magnate Mikhail Khodorkovsky.

"The witness hasn't come," Judge Viktor Danilkin said in the courtroom. "The reason is unknown."

Bogdanchikov was supposed to tell the court about the oil industry and vertically integrated oil companies such as Rosneft and now-defunct Yukos.

Prosecutors accuse Khodorkovsky and his business partner Platon Lebedev of theft from affiliated companies when the men ran Yukos.

Rosneft spokesman Nikolai Manvelov said the company wouldn't comment on why its chief ignored the court.

If Bogdanchikov doesn't provide a good excuse for not appearing in court, the court may fine him or order him convoyed to the courtroom for testimony, said defense lawyer Vadim Klyuvgant, Interfax reported.

Khodorkovsky and Lebedev are undergoing a trial for a new set of charges on top of the fraud and tax evasion for which they are currently serving an eight-year prison sentence that began in 2003.