Turkey Blocks, an organisation that monitors Internet censorship in the country, tweeted on Friday night that Facebook, Twitter and YouTube were being blocked. 

Both Vimeo and Instagram remained live during that period. The group later tweeted saying 

"Our data indicated a 2 hour period of social media throttling but no evidence of a full internet blackout in #Turkey." 

Internet censorship is not unheard of in Turkey. It occurs when the government orders internet service providers to block particular domains, according to Access Now, a digital rights group.

It was unclear if the outage was caused by a surge in use or as a result of government censorship.

We have no reason to think we’ve been fully blocked in #Turkey, but we suspect there is an intentional slowing of our traffic in country.

— Policy (@policy) July 15, 2016

A spokesperson from YouTube denied its service had been impacted and told the media

"We are aware of reports that YouTube is down in Turkey, however, systems seem to be functioning normally."

History

The issue of Internet censorship features heavily in the country's history, with three outages taking place earlier this year. The most recent of these outages took place following the terror attack on Ataturk Airport in Istanbul. 

"Turkey spent years building up its filtering capacity to block specific sites and content, as well as amending its internet law to increase government's control over content online," explains Peter Micek, global policy and legal counsel at Access Now. 

The country passed an internet censorship law in 2007 that allows the government to ban or block websites. This law was initially aimed at blocking child abuse images, but these controls have been used in moments of political unrest. 

Turkish president Recep Tayyip Erdogan is heavily critical of social media. He described Twitter as a "menace to society" back in 2013.