BEIJING - CHINA'S former finance minister Jin Renqing has been detained, Hong Kong's Ming Pao Daily News reported, despite officially having been transferred to a post at a think-tank.

Jin, 63, was a few years short of mandatory retirement from a ministerial post, when he was sacked last month and demoted to deputy director at the State Council Development Research Centre, a position with vice-ministerial rank.

He has not shown up at his new post because he is 'required to assist the investigations of relevant departments', the paper said on Saturday, citing sources at the centre.

His name is not listed on the Centre's website.

Jin left the Finance Minister post for 'personal reasons' a State Council Information Office spokesman said in August.

The finance minister in China plays more of an administrative role managing the country's finances, rather than driving policy, which is usually set by leaders at the vice-premier level or higher.

Media speculated that Jin's departure was linked to a sex scandal or questionable dealing.

A person can be detained indefinitely in China to 'assist' in investigations, during which time they generally have no contact with family members, lawyers or any other associates.

The detention period often ends with a formal charge. -- REUTERS