Dutch media found evidence that the "overseas service stations", which promise to provide diplomatic services, are being used to try to silence Chinese dissidents in Europe, BBC reported.

A spokeswoman for the Dutch foreign ministry told BBC the existence of the unofficial police outposts was illegal.

The Chinese foreign ministry has denied all allegations leveled by the Netherlands.

The investigation was sparked by a report entitled Chinese Transnational Policing Gone Wild, by the Spain-based NGO Safeguard Defenders.

According to the organisation, the public security bureaus from two Chinese provinces had established 54 "overseas police service centres" across five continents and 21 countries.

Most of them are in Europe, including nine in Spain and four in Italy. In the UK, it found two in London and one in Glasgow.

The units were ostensibly created to tackle transnational crime and conduct administrative duties, such as the renewal of Chinese drivers' licences. But, according to Safeguard Defenders, in reality they carry out "persuasion operations", aimed at coercing those suspected of speaking out against the Chinese regime to return home, reports BBC.