Facebook incorrectly removed a post critical of the prime minister’s comments regarding slavery in Australia that featured a photograph of Aboriginal men in neck chains from the late 1800s, claiming the photo featured nudity.

On Thursday, Scott Morrison said that there was no slavery in this country.

On Friday he backed down from those comments and acknowledged the history of blackbirding in Australia – where people were coerced into working as indentured labourers, often through deception or force. He said his Thursday comments related to the principles that existed when the colony of New South Wales was founded – that there was to be no lawful slavery in Australia.

Following his comments on Thursday, debate on social media was rife with discussion of Australia’s history of slavery. One Australian user posted about the topic on his personal Facebook profile, including a photo of nine Aboriginal men chained together by their necks wearing loin cloths outside Roebourne Gaol in 1896.

“Kidnapped, ripped from the arms of their loved ones and forced into back-breaking labour: The brutal reality of life as a Kanaka worker - but Scott Morrison claims ‘there was no slavery in Australia’,” the post stated.”

The photo from the state library of Western Australia refers to the men as prisoners, and the photo had been shared in stories about Morrison’s comments in the Daily Mail.

The post was removed by Facebook, and the man had his account restricted, with Facebook claiming the photo contained nudity and was in breach of the social media site’s community standards.

The post was restored after Guardian Australia asked Facebook about whether the photo had been flagged in error. Facebook apologised to the user late on Friday and restored the post.

A spokeswoman for Facebook said the photo was removed by the automated system in error.

“We apologise for this mistake,” she said.

As of Saturday morning, Facebook was blocking users from sharing Guardian Australia’s story based on its use of the image.

According to Facebook’s latest community standards report, between January and March this year, Facebook removed 39.5m pieces of content for adult nudity or sexual activity, and of that 99.2% was removed by Facebook automatically, without a user reporting it.

Through the appeals process Facebook has in place, there were 2.5m appeals made, and 613,000 pieces of content were restored.

In 2016, Facebook backed down on a ban on the famous photo of nine-year-old Kim Phúc running away from a napalm attack during the Vietnam war on the grounds of the nudity in the photograph, after a strong backlash over claims of censorship.

Facebook also faced criticism in Australia in 2016 for blocking the account of Arrente writer Celeste Liddle four times after she shared a trailer for an Indigenous comedy show that featured images of topless desert women. Trolls kept reporting the content as “indecent”, and Facebook kept removing the trailer and locking Liddle out of her account.