Istanbul, April 6 () - Turkish authorities have blocked access to Twitter, YouTube and Facebook over the publication of photos published on the three social media platforms showing a prosecutor who was taken hostage by militants in Istanbul last week.

Tayfun Acarer, the head of the Information and Communications Technologies Authority (BTK), told daily Hürriyet that the ban on Facebook had been lifted.

A number of Turkey's leading Internet service providers implemented the ban in the afternoon of April 6, an official confirmed after widespread complaints about access problems to the social media websites.

Speaking to daily Hürriyet, Internet Service Providers Union (ESB) Secretary General Bülent Kent stressed that "the procedure continues" as all service providers are expected to implement the ban soon.

A recent court ruling seen by daily Hürriyet ordered authorities to block a total of 166 websites that published the controversial photos. Beside the world's largest social media websites in the list, there are also specific links to the stories published by Turkish newspapers.

Two militants with alleged links to the outlawed far-left Revolutionary People’s Liberation Party-Front (DHKP-C) took Mehmet Selim Kiraz, the prosecutor in the controversial case of the killing of Gezi victim Berkin Elvan, hostage in Istanbul's Çağlayan Courthouse on March 31.

Kiraz succumbed to his injuries in hospital after the eight-hour hostage drama, during which security forces killed the two captors.

On April 1, a total of 13 media organizations and journalists had their access banned for the press conference and the funeral ceremony of Kiraz at the Eyüp Sultan Mosque on April 1 for publishing photos showing Kiraz as a hostage.

Turkish Prime Minister Ahmet Davutoğlu later announced that he gave the instruction to withhold accreditation.

Separately, an criminal investigation into seven Turkish newspapers for publishing the hostage photo was launched on April 2.