The Guardian appeared to be partially blocked in China on Wednesday after revealing that relatives of the country's top political and military leaders are making use of offshore companies in the Caribbean.

The report, based on leaked financial documents, showed that the brother-in-law of president Xi Jinping and son and son-in-law of former premier Wen Jiabao were among more than a dozen family members of current or former leaders using the offshore havens.

Repeated attempts to access the story from China failed without a virtual private network (VPN). Some attempts to reach The Guardian’s front page failed and access to other, unrelated stories was intermittent.

Earlier this month, The Guardian was briefly partially blocked before becoming accessible again.

The report that more than 21,000 clients from China and Hong Kong have made use of the Caribbean offshore havens is the latest revelation in a two-year initiative by the International Consortium of Investigative Journalists, which has shared leaked data from two companies in the British Virgin Islands with the Guardian and other international news organisations.

The website of the ICIJ could not be reached and the website of the Spanish newspaper El Pais, another of the media partners, also appeared to be inaccessible.

Australia’s Global Mail could be accessed, but not its story about the wealth. Reports on the holdings could be read in full on the websites of France’s Le Monde, Germany’s Suddeutsche Zeitung and Canada’s CBC News.

The wealth of Chinese officials and their families has become a subject of growing interest, particularly in light of Xi’s campaign for austerity and against corruption since becoming leader.

Chinese activists whose campaigns have included a push for financial transparency – holding street protests calling on officials to declare their assets – have faced a punishing crackdown. Xu Zhiyong, the best-known member of the New Citizens Movement, is standing trial in Beijing on Wednesday while other members of the movement will be tried on Thursday and Friday.

The websites of Bloomberg and the New York Times have been blocked in China since they reported on the onshore assets of relatives of leaders – including those of Xi and Wen – in 2012. They have also been unable to obtain visas for new reporters.

Austin Ramzy, who has worked on the mainland for several years and sought to transfer to the New York Times from another publication, will have to leave when his current visa runs out at the end of the month unless the authorities change course.