Liu Jianchao, head of a department under the ruling Communist Party that oversees relations with foreign political parties, was "taken away" after returning to Beijing from a work trip abroad in late July, according to people familiar with the matter, the report said.

The reason for his detention could not be determined, it added.

China's foreign ministry did not immediately respond to a request by AFP to confirm the report.

Liu, 61, has previously served in key diplomatic roles including ambassadorships to the Philippines and Indonesia and foreign ministry spokesperson.

He has also led various national and regional bodies tasked with implementing President Xi Jinping's signature crackdown on corruption.

His detention represents the highest-level inquiry into a Chinese diplomat since Qin Gang, who was removed as foreign minister in 2023 following reports of an extramarital affair.

Liu has been widely viewed as a rising figure in the Chinese diplomatic world.

In early July, he accused the United States' defence chief of "inciting confrontation and conflict" by urging American allies to bolster their militaries to counter China.

His most recent public engagement was on July 29 in Algeria, following meetings in several African countries, Singapore and elsewhere late last month, according to the website of the International Department, which he currently heads.