A former executive of the beleaguered oil giant Yukos, Alexei Pichugin, was sentenced to 20 years in jail for murder yesterday, as the trial of company founder Mikhail Khodorkovsky draws to a close.

A Moscow City Court jury had found Mr. Pichugin, once a top security officer for Yukos, guilty of organizing a double murder in 2002 as well as an attack on the head of the Moscow mayor’s communication service.

Prosecutors had originally requested a life sentence for Pichugin. His prison term will be counted from his arrest in July 2003.

Pichugin has dismissed the charges as part of a Kremlin-instigated crackdown on Yukos. His lawyers vowed to appeal the verdict, saying there were numerous procedural violations, including what they described as an illegal decision to end the trial.

“Not a single classified document has been presented at the trial,” said a defense lawyer, Ksenia Kostromina.

Pichugin’s lawyers also said that the indictment was based on the testimony of convicted criminals serving prison sentences for murders and rapes.

“The criminal case doesn’t contain evidence that would prove his involvement in those crimes,” Pichugin’s chief lawyer, Georgy Kaganer, said at a news conference.

Another attorney, Dmitry Kurenin, said prosecutors could not prove beyond a doubt that the husband and wife Pichugin was convicted of killing were even dead.

“They never have proven that these people had been killed,” Mr. Kurenin said, claiming that blood samples used by prosecutors didn’t match those of the alleged victims.

Lawyers also said investigators were urging Pichugin to testify against Mr. Khodorkovsky and other Yukos officials.

The legal attack on Yukos and top executives is widely seen as the Kremlin’s effort to establish control over strategic energy assets and punish Mr. Khodorkovsky for his perceived political ambitions. The company, once the largest Russian oil producer, has been dismantled to pay off a $28 billion tax bill.

President Putin has repeatedly contended that the investigations of Mr. Khodorkovsky and Yukos targeted a rotten business empire and its owners.

Prosecutors on Tuesday demanded maximum 10-year prison sentences for Mr. Khodorkovsky and his co-defendant Platon Lebedev. Mr. Khodorkovsky has been in jail since October 2003, facing trial on fraud and tax-evasion charges.

Also yesterday, tax authorities levied a $647 million bill against Messrs. Khodorkovsky and Lebedev for what they said were unpaid taxes.

Federal Tax Service official Alexandra Nagornaya told the court that the pair used front companies registered in onshore tax havens to dodge corporate taxes as well as illegally using promissory notes to pay tax bills. Messrs. Khodorkovsky and Lebedev had additionally avoided paying nearly $4 million in personal income tax, she said.