A warning that Muslim extremists could attack members of the military in Australia has gone out to army officers, highlighting the case of one officer who was verbally abused in Sydney’s CBD, it’s been reported.

The warning of such a terrorist attack went out just 48 hours before Australia on Friday increased the public terrorism alert to High, News Corp Australia reported on Sunday.

It says the Defence Security Authority, which advises the Chief of the Defence Force on how to manage security risks in Australia, warns in the memo of the need to be vigilant and report any verbal threats.

Marked Security Intelligence Report, the memo details verbal threats made against a uniformed officer who was approached by a group of young men and told to go to the Middle East so we can “blow your f***in head off”, media outlets report.

The incident was reportedly witnessed by a large group of people but the ADF member walked away from the scene.

The memo underlined the risks of an attack such as that on British army soldier, Fusilier Drummer Lee Rigby, who was run down by a car then hacked to death on a London street by Muslim extremists in May last year.