The United States has issued a health alert to Americans in China after reports of a "sonic attack" on one of its diplomatic staff.

The US State Department said the government employee suffered a mild traumatic brain injury after experiencing "abnormal" sensations of sound and pressure, similar to the wave of so-called "sonic attacks" on its diplomats in Cuba.

In a health alert issued on Wednesday, officials said an employee based in the southern Chinese city of Guangzhou reported “subtle and vague, but abnormal, sensations of sound and pressure.”

"The US government is taking these reports seriously and has informed its official staff in China of this event," the US consulate said in an email to American citizens.

The notification said the department was not aware of any other cases inside or outside the diplomatic community.

But in an indication of how worried officials are, the US embassy in Beijing and all five US consulates in China held meetings yesterday to allow their staff to ask questions and raise concerns.

Mike Pompeo, the Secretary of State, told Congress yesterday: “The medical indications are very similar, and entirely consistent with, the medical indications that were taking place to Americans working in Cuba”.