It says the internal ministry report will be handed over to the police for further study and action.

Public Service Department director-general Mohd Shafiq Abdullah says they will undergo courses to increase their skills, which is a common practice at the ministry.

The decision was taken in response to the expulsion by Washington of Russian diplomats at the UN in New York, the source says.

Russia's invasion has uprooted more than 2 million people in what the United Nations calls the fastest humanitarian crisis in Europe since World War Two.

The US mission to the UN described the Russian diplomats as 'intelligence operatives' who had been 'engaging in espionage activities that are adverse to our national security.'

US citizens 'who are visiting or residing in Russia have been interrogated without cause, and threatened by Russian officials and may become victims of harassment, mistreatment, and extortion,' the advisory says.

In the European Union, countries such as France have sought a common EU response but the bloc is torn over whether to join the diplomatic boycott, fearful of Chinese retaliation that would hurt trade.

Cases of Havana syndrome first surfaced in 2016 in the Cuban capital, with US and Canadian diplomats complaining of severe headaches, nausea and possible brain damage after hearing high-pitched sounds.

A Japanese government spokesman says the Myanmar embassy has told the foreign ministry that diplomatic visas for the pair will no longer be valid.

It is understood that at least three former ministers have been silently campaigning for diplomatic jobs.