Three people have been killed during a five-hour gunbattle between police and militants in Istanbul.One policeman and a civilian died in the siege along with the leader of a ultra-leftist group known as the ‘Revolutionary Headquarters.’ The organisation is believed to have links with Kurdish separatists. Heavily armed special forces tried to storm the apartment block on the Asian side of the city early this morning. At the height of the battle, smoke billowed from the block where many residents were trapped. Several other people, — police and civilians — were injured in the fire fight. The raid was one of more than 60 carried out overnight as part of a crackdown against radical Kurdish and Islamist groups.