UPDATE 1-Tunisia to investigate Mahdi Organisation over Nice attack -state media

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TUNIS, Oct 30 (Reuters) - Tunisian authorities have authorised an investigation into whether a group called the Mahdi Organisation exists and carried out the Nice attack, based on social media claims of responsibility, state news agency TAP reported on Friday.

The public prosecutor's office of the judiciary's anti-terrorism court has delegated a specialised security unit to carry out the investigation, TAP reported.

It will seek to learn whether the Mahdi organisation exists and the veracity of claims made on social media that it was behind Thursday's attack in the French city, it reported.

The suspect in the attack, in which an assailant shouting "Allahu Akbar" (God is Greatest) beheaded a woman and killed two other people in a church, is Brahim Aouissaoui, a 21-year old Tunisian who had recently emigrated to Europe. (Reporting by Tarek Amara; Editing by John Stonestreet and Catherine Evans)