Two more members of China's top leadership have been caught up in the growing global controversy over offshore companies after it was revealed that their relatives used the services of Mossack Fonseca, the Panamanian law firm that has helped global political elites manage their fortunes.

In its latest "Panama Papers" revelations, the International Consortium of Investigative Journalists said that in-laws of Zhang Gaoli and Liu Yunshan were shareholders in companies incorporated in the British Virgin Islands. Mr Zhang, executive vice-premier, and Mr Liu, the ruling Chinese Communist party's propaganda head, both sit on the seven-member Politburo Standing Committee, China's most powerful body.

It was not clear what assets Mr Zhang's son-in-law, Lee Shing Put, and Mr Liu's daughter-in-law, Jia Liqing, controlled through the BVI vehicles.

The revelation brings to three the number of Standing Committee members with relatives cited in the Panama Papers. In its initial report, the ICIJ said that Deng Jiagui, Mr Xi's brother-in-law, was among Mossack Fonseca's clients. Mr Deng's wealth was first revealed by Bloomberg in 2012.

The ICIJ's findings have been dismissed as "groundless" by China's foreign ministry.

Ownership of an offshore company is not illegal in China and none of the three leaders' relatives have been accused of wrongdoing. But the revelations are potentially embarrassing given the sweeping anti-corruption campaign launched by Mr Xi three years ago. Reports about the Chinese leadership's Panama Papers connections have been blocked by government censors, who report to Mr Liu.