The pilot scheme, designed to rein in debt risks among financial holding companies, also included retail conglomerate Suning.com and large state-owned companies such as China Merchants Group, Shanghai International Group, and Beijing Financial Holdings Group, state news agency Xinhua reported late on Friday.

Based on the trial, the People's Bank of China (PBOC) aims to roll out a supervision plan for the broader sector as soon as in the first half of 2019, Xinhua said.

Zhou Xuedong, director of the PBOC's Financial Stability Bureau, said some financial holding companies had grown through "barbaric" expansion and a regulatory void needed to be filled urgently.

"They are large in volume with complex businesses and high association risks, and the lack of supervision would increase risks in the financial sector," Zhou was quoted by Xinhua as saying.

The PBOC has pledged to speed up efforts to regulate financial holding companies' high-leverage investments and strengthen supervision over their transactions, it said in a Financial Stability report released on Friday.

The PBOC is adopting "a combination of macro-prudential management and micro-prudential supervision" in its regulatory approach, but no details were given according to Xinhua.

Shares in Suning.com fell as much as 1.5 pct around midday as investors worried about tighter regulations and a slowing economy that threatens to curb spending.

Suning did not immediately respond to a request for comment.

Ant Financial declined to comment.

Reuters reported in June that Ant Financial was singled out by the PBOC as the only online finance firm for a trial programme to test stricter regulations on financial holding conglomerates, according to two sources.

(Reporting by Yawen Chen and Ryan Woo; Additional Reporting by Lusha Zhang, Shu Zhang and Pei Li; Editing by Sam Holmes and Darren Schuettler)