Beijing has stepped up espionage warnings in recent years as relations with the United States and other Western nations have worsened.

Chinese authorities found "irrefutable evidence" of efforts by the US National Security Agency (NSA) to hack the National Time Service Center, between 2022 and 2024, according to a statement published on the official Ministry of State Security WeChat account.

The facility is responsible for coordinating clocks around the country used by everything from computer servers to train stations and power grids.

The ministry accused the NSA of exploiting weaknesses in the messaging service of an unspecified foreign mobile phone brand in order to steal login credentials from employees at the time centre.

The attacks could have jeopardised power grids, transport, and even space launches, the ministry said.

Chinese authorities have since "severed attack chains, upgraded protective measures, and eliminated potential threats."

"In recent years, the United States has aggressively pursued cyber hegemony, repeatedly trampling on international cyberspace rules," the ministry said in its statement.

It urged Chinese citizens to be vigilant of foreign attacks and to report suspicious activity to the authorities.

Western countries have accused hacker groups allegedly supported by China of conducting a global cyber espionage campaign against figures critical of Beijing, democratic institutions, and companies in various sensitive sectors.

Washington said last year that a China state-sponsored actor was behind a cyber breach at the US Treasury Department.

Beijing at the time called the accusations "groundless".

"Ironclad evidence proves that the United States is the true 'hacker empire' and the greatest source of chaos in cyberspace," the Chinese Ministry of State Security said Sunday.