US Vice-President Kamala Harris’s flight to Vietnam was delayed by several hours due to an “anomalous health incident” with similarities to so-called Havana syndrome, reports say.
The mysterious syndrome first affected people at the US and Canadian embassies in Havana in 2016 and 2017. It may be caused by directed microwave radiation.
Ms Harris was in Singapore ahead of her visit to Vietnam at the time of the incident in Hanoi.
It is unclear who was affected.