Australia’s defence department has defended the level of security at a key Sydney naval base after footage on Chinese social media appeared to show a public drone landing on a navy vessel.

The footage, understood to be several years old, was posted on social media site Weibo and appears to have been captured by a drone that flew above Australian warships – even landing on one – docked at Sydney’s Garden Island base.

Located in Sydney Harbour, the base is about 1km to the east of the Sydney Opera House.

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In a statement, a defence spokesperson said the department was aware of the social media post and confirmed the footage over Fleet Base East was “several years old”.

“Defence employs robust and layered security measures to protect its ships and establishments,” the spokesperson said.

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The Garden Island defence precinct has existed in Sydney Harbour since the 1880s and is regarded as one of Australia’s most important naval bases.

“Given its central location, some activity in the Garden Island defence precinct can be observed by the general public. Measures to protect sensitive information are taken accordingly,” the spokesperson said.

The regulator that oversees drone regulations, Civil Aviation Safety Authority (Casa), prohibits the flying of drones over Fleet Base East, the spokesperson said.

Casa was contacted for comment.

In response to claims that police had spoken with the person who flew the drone and recorded the footage, a New South Wales police spokesperson said the matter had been referred to the defence department.

The defence minister, Richard Marles, and the Australian federal police were contacted for comment.