Lee was sentenced in a Seoul court on Friday on charges of bribery, embezzlement and abuse of power, and ordered to pay a 13 billion won ($11.5m; £8.8m) fine.

The former president claims the charges are politically motivated.

He becomes the fourth South Korean former leader to be jailed, following his successor's imprisonment in April.

Park Geun-hye was sentenced to 33 years in jail after being found guilty of abuse of power and coercion.

The judge at Seoul Central District Court said "heavy punishment for the accused is inevitable" because of the serious nature of the crimes.

The court found the former leader accepted billions of won from major electronics firm Samsung in return for pardoning its chairman, Lee Kun-hee. The company denies having given the former president the money.

Links between political leaders and large family-owned conglomerates known as chaebols have often come under scrutiny, or been the focus of criminal allegations.