Broadcom-owned VMware, Palo Alto Networks and Fortinet are among the US firms whose cybersecurity software has been banned, while Check Point Software Technologies is among the Israeli companies, they said.

Reuters was not able to establish how many Chinese companies received the notice, which the sources said was issued in recent days.

Chinese authorities expressed concern that the software could collect and transmit confidential information abroad, said the sources, who declined to be named due to the sensitivity of the situation.

China’s internet regulator, the Cyberspace Administration of China, and the Ministry of Industry and Information Technology had not responded to requests for comment at the time of publication.

The four companies also did not reply to Reuters queries.

As the US and China battle for tech supremacy amid heightened trade and diplomatic tensions, Beijing has been keen to replace Western-made technology with domestic alternatives.

While its efforts to build up its semiconductor and artificial intelligence sectors have dominated headlines, it has also sought to replace Western computer equipment and word processing software.

Chinese analysts have also said that Beijing has become increasingly concerned that Western equipment could be hacked by foreign powers.