By Ahmed Rasheed BAGHDAD (Reuters) - Iraqi security forces said they advanced to within 2 km (1.2 miles) of the city of Baiji on Wednesday in a new offensive to retake the country's biggest oil refinery, besieged since June by Islamic State militants. Backed by Shi'ite militias and army helicopters, government forces have swept through a desert area to the west of Baiji, aiming to recapture the city 200 km (130 miles) **rth of the capital. ...