Turkish media say a policeman has been stabbed to death in Istanbul by a suspected Islamist militant who was in custody.<br /><br />The state news agency Anadolu said the aggressor had been driven to police headquarters and was being taken to his cell when he struck.<br /><br />He was immediately shot dead by the security forces.<br /><br />The man suspected of links to the so-called Islamic State had been detained because he was suspected of preparing an attack.<br /><br />The officer, named as Sinan Acar, was taken away by ambulance but died in hospital. Despite a temporary media blackout over the attack a crowd gathered outside.<br /><br />There are questions over why apparently his attacker had not been handcuffed.<br /><br />Turkey has been struck by several fatal attacks attributed to ISIL, the last one being at New Year.<br /><br />Suspects are regularly arrested; on Saturday four were detained west of Istanbul. <br /><br />State media said they were on a mission to plan an attack.<br />
