Another 'sonic' attack against US diplomats at the embassy in Havana is feared to have taken place in August.

The newest incident is said to have affected another three diplomats, bringing the total number of people harmed to 19.

It comes after a spate of attacks between November 2016 and April 2017 which left 16 diplomats suffering severe health problems.

Some lost their hearing and others suffered mild brain injuries as a result of the undetected attacks which authorities fear took place at their homes or nearby.

It is not clear where exactly the most recent incident occurred.

The incident is said to have taken place in August. Pictured, the US Embassy in Havana

All are being investigated by the State Department which fears it may discover more yet.

'We can't rule out new cases as medical professionals continue to evaluate members of the embassy community,' state department spokeswoman Heather Nauert said on Friday.

Two Cuban diplomats were expelled from Washington after the attacks came to light.

They are feared to have been caused by a subtle sonic device which can cause deafness.

The embassy in Havana reopened in 2015 after decades of hostility between the US and Cuba.

Diplomats complained of symptoms including severe headaches and dizziness.

They are believed to have taken place either inside or near their residences.