Filipino troops began driving the country’s Isis affiliate from southern city of Marawi in earnest on Thursday. Backed by tanks and helicopter gunships, soldiers fought their way into the city of 200,000 inhabitants on the main southern island of Mindanao. Military spokesman Lieutenant Colonel Jo-ar Herrera said: "Attack helicopters fired rockets in a precision attack. We want to finish this problem as soon as possible." Reporters heard gunfire and saw plumes of smoke rising from the centre of the cordoned-off city as choppers roared overhead. Col Herrera said some 21 people had been killed so far, including 13 Abu Sayyaf gunmen and five soldiers. Lanao del Sur province Vice-Governor Mamintal Alonto Adiong said more than half the city’s population had fled. Abu Sayyaf seized the city on Tuesday night after a failed security forces raid to capture the extremists’ commander and preacher Isnilon Hapilon. They torched the city’s cathedral, took 14 hostages includi