Photo-sharing site Instagram has been fully restricted in China as a result of it being used topublicise images of civil unrest in Hong Kong during which riot police clashed with protestors - before suppressing them with tear gas.

In a bid to stop the pro-democracy movement from growing, Chinese authorities have blocked access to the site and mentions of the phrases 'OccupyCentral' and 'OccupyHK' have been censored across other prominent social media sites such as Weibo, according to Reuters.

The demonstration, which is now in its third day, was first launched as a student sit-in to protest the lack of reforms in the semi-autonomous region.

The Facebook subsidiary had escaped Chinese censors until this point - one of the few western social networks to do so.

Although the site remains operational in Hong Kong, it has been fully blocked in China in a bid to stop the unrest from spreading.

Web access tool blockedinchina.net confirmed that the photo-sharing site was blocked in the region.

This move deprives Chinese web browsers from seeing thousands of images taken by protestors in a movement which has now gained substantial international coverage.

An Instagram spokesperson said: “We are aware of reports and are looking into it."

Topically, last week, Twitter chief executive Dick Costolo tweeted Iranian president Hassan Rouhani requesting that he removed the country's block on the social network which has been in place since 2009.