Google says it is "appalled" and has apologised to a black couple after the firm's new Photos app mistakenly labelled them as "gorillas".

The app uses artificial intelligence to scan and identify subjects in images before labelling them. Software developer Jacky Alcine brought the issue to Google's attention on social media when he shared a photo of himself and a female friend, which was labelled "gorillas" in the tags section of the app.

Google executive Yonatan Zunger replied: "This is 100% not OK. (It was) high on my list of bugs you never want to see happen."

Mr Zunger added that steps were being taken to avoid other incidents of mistaken tagging.

"We're also working on longer-term fixes around both linguistics (words to be careful about in photos of people) and image recognition itself (eg, better recognition of dark-skinned faces). Lots of work being done, and lots still to be done. But we're very much on it."

In a further statement to the BBC, Google said: "We're appalled and genuinely sorry that this happened."

It is not the first time the Photos app, launched by Google earlier this year, has been criticised for getting labels on images wrong. In May, news website iTech Post reported that the app was tagging some images of dogs as horses.

However, users are able to remove badly chosen tags manually, and the Photos app is able to note these change and improve accuracy over time and increased use - a type of technology known as machine learning.

But Google acknowledged the severity of the incident, adding that "immediate action" was being taken to prevent this type of mistake happening again.