Two men working in the telecommunications industry have been arrested in Poland on suspicion of espionage.
A Chinese employee of Huawei and a Polish man, who is reportedly a former counter-intelligence officer, have been taken into custody.
The Chinese foreign ministry said it was “highly concerned” about the arrest of its national.
The pair are likely to be held for three months before the case progresses, said state news agency PAP.
According to the country’s public broadcaster TVP, neither have pleaded guilty but both have reportedly refused to explain themselves to investigators.
Maciej Wasik, the deputy head of Poland’s special services, said: “The Chinese national is a businessman working in a major electronics company … the Pole is a person known in circles associated with cyber business.”
The Polish national, named by TVP as “Pior D”, was reportedly a former employee of Orange.
In a statement, Orange announced that the Polish internal security agency gathered materials from its office on Tuesday in connection to an unnamed employee.
Huawei said it was “aware of the situation” and “looking into it”.
The company said: “Huawei complies with all applicable laws and regulations in the countries where it operates, and we require every employee to abide by the laws and regulations in the countries where they are based.”
Last month, US prosecutors charged Huawei’s chief financial officer, Meng Wanzhou, with fraud.
It is alleged she used Hong Kong company Skycom to access the Iranian market in deals that violated US sanctions.
Separately, authorities in the US, UK, Australia, Canada and New Zealand have spoken about Huawei’s telecommunications equipment as posing a potential espionage risk to their national networks.
Security threats from Chinese companies building 5G networks could end up “putting all of us at risk” if they are not tackled quickly, a former UK security minister warned last year.
Speaking to Sky News, Admiral Lord West, a former First Sea Lord who served under Gordon Brown as a security minister, urged the government to set up a unit reporting directly to the prime minister to monitor the risk posed by Chinese equipment in 5G.
5G has been hailed as the next great leap for mobile communications, enabling everything from smart cities to hologram calls.
However, the best 5G technology comes from Chinese companies, raising the fear that China’s government could have ground-level access to – even control of – the UK’s critical data infrastructure.