A South Korean appeals court on Friday upheld a four-year prison term imposed on the head of the country's third-largest conglomerate, SK Group, for embezzling company funds.

Chey Tae-won, 53, was found guilty of embezzling nearly 50 billion won (US$45 million) from two SK Group affiliates and funneling the funds to make personal investments in stock futures and options in 2008.

In the same ruling, the Seoul High Court overturned an acquittal of Chey Jae-won, the chairman's younger brother and the group's vice chairman, and sentenced him to three years and six months behind bars for conspiring with the elder Chey.

The 50-year-old vice chairman was sent to prison from a courtroom after the verdict was handed down. The chairman has been imprisoned since January.

"The nature of the defendants' crimes is very offensive as they used the funds of SK Group affiliates as the means of their crime to fulfill their greed," Judge Moon Yong-seon said in the ruling.

The court's decision came despite a recent dramatic extradition of a key figure in the case. On Thursday, Kim Won-hong, who has been accused by Chairman Chey as the main culprit behind the massive embezzlement scheme, was extradited from Taiwan.

The Seoul High Court, however, turned down the brothers' demand to postpone the sentencing trial to further hear from Kim. It questioned Kim's credibility as a witness.

The court also raised doubt over the previous crime record of Chairman Chey and said that he has not shown sincere remorse.

The elder Chey was previously sentenced to three years behind bars in 2003 for accounting fraud and illegal stock trading. However, he was released on bail the same year.

In the past, powerful tycoons rarely spent any time in prison, as courts often did not arrest them and even handed down suspended prison terms citing their importance to the national economy.

SK Group has more than 90 affiliates, mainly in the fields of energy and telecommunications. (Yonhap News)