BEIJING (AFP) - Secretary of State Mike Pompeo said on Wednesday (May 23) that the brain injury sustained by an American official in China was "very similar" to those that affected US and Canadian diplomats in Cuba.

The US embassy in China issued a health alert on Wednesday after a US government employee who had experienced an "abnormal" sound was diagnosed with mild traumatic brain injury (MTBI).

"The medical indications are very similar and entirely consistent with the medical indications that have taken place to Americans working in Cuba," Pompeo told the House Foreign Affairs Committee.

Pompeo said the US was moving medical teams to the area to work on the case.

"We are working to figure out what took place both in Havana and now in China as well," Pompeo said.

He said the Chinese government has committed to helping in the case, under its responsibility to protect foreign diplomats.

In the alert e-mailed to US citizens in China, the embassy said it did not know what had caused the symptoms or of any similar situations in the country.

In Cuba last year, the US disclosed that 24 diplomats and their family members had fallen victim to an unsolved mysterious attack that left them with injuries resembling brain trauma. Ten Canadian diplomats and their relatives also suffered a strange illness.

"We cannot at this time connect it with what happened in Havana but we are investigating all possibilities," a US embassy official in Beijing told Agence France-Presse on the condition of anonymity.

The embassy's health alert says the government employee, who was assigned to the southern city of Guangzhou, "recently 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 message says.

"While in China, if you experience any unusual acute auditory or sensory phenomena accompanied by unusual sounds or piercing noises, do not attempt to locate their source. Instead, move to a location where the sounds are not present," it says, urging people with medical problems to consult a doctor.

Embassy spokesman Jinnie Lee said the employee experienced "a variety of physical symptoms" between late 2017 through April 2018. The person was sent to the United States and diagnosed with MTBI on May 18.

"The (State) Department is taking this incident very seriously and is working to determine the cause and impact of the incident," Ms Lee said.

"The Chinese government has assured us they are also investigating and taking appropriate measures."

In Cuba, the American victims had associated the onset of their symptoms with "unusual sounds or auditory sensations", a State Department physician told the US Senate in January.

Dr Charles Rosenfarb, a doctor and director of the State Department bureau of medical services, said the symptoms were mixed but consistent with brain trauma.

The victims suffered headaches, hearing loss, disorientation and some loss of cognitive ability.

Initially officials suspected the Americans had been targeted by some sort of acoustic weapon, although senior officials were more cautious in public, speaking of "health attacks".

Media reports have suggested that the FBI has not been able to verify any evidence to support the sonic weapon theory.

The US government has held Cuba responsible, arguing that Raul Castro's authoritarian state must have either carried out the assaults or at least known who was behind them.