Samsung heir Lee Jae-Yong has been sentenced to five years in prison for bribery, perjury and other crimes.

The Seoul Central District Court on Friday convicted Lee, 49, the vice-chairman of Samsung Electronics, the world's largest smartphone maker, of offences related to the corruption scandal that brought down ousted president Park Geun-Hye.

Lee Jae-Yong's penalty could leave the giant firm rudderless for years and hamper its ability to make key investment decisions.

Lee Jae-Yong, the son of Samsung group chairman Lee Kun-Hee, has been groomed all his life to take over the giant conglomerate founded by his grandfather in 1938. It is by far the largest of the chaebols, the family-controlled firms that dominate Asia's fourth-largest economy, which some South Koreans self-mockingly dub the “Republic of Samsung”. Its turnover is equivalent to a fifth of the national GDP and it has long had close, opaque connections with political authorities.

Prosecutors had demanded a 12-year sentence for Lee Jae-Yong. The vice-chairman of Samsung Electronics stepped from a justice ministry bus handcuffed, bound with white rope around his dark jacket, and carrying an envelope of documents as he walked into Seoul Central District Court.

Lee, 49, was facing multiple charges including bribery, embezzlement and perjury stemming from the scandal, centred on payments and promises by Samsung around $40 million to Park Geun-Hye's secret confidante Choi Soon-Sil.

Prosecutors had said that the money was in return for policy favours including government support for Lee's hereditary succession at the group, after his father was left bedridden by a heart attack in 2014.

The defence, however, said that it was pressured by Park Geun-Hye to make the donations under duress — and that Lee was not aware of them and did not approve them.

The demonstrators who mounted giant candlelit protests against Park Geun-Hye last year also targeted Lee and other chiefs of the chaebols, as the family-controlled conglomerates that dominate Asia's fourth-largest economy are known.

Around 800 riot police were deployed around the Seoul Central District Court to prevent possible clashes between rival sets of demonstrators, the Yonhap news agency reported. The court refused permission for the verdict to be broadcast live, in contrast to the Constitutional Court's ruling on Park Geun-Hye's impeachment in March.

It was deluged with hundreds of applications for the 30 seats in courtroom 417 available to members of the public, which were allocated by lottery.

Park Geun-Hye's own trial began in the same room in May, and it also saw Lee's father Lee Kun-Hee convicted of tax and other offences in 2008, receiving a suspended sentence.