Joint Iraqi forces backed by international coalition's fighter jets liberated Friday Baiji's district center in Saladin province, northern Iraq, killing 52 Islamic State (IS) militants, Iraqi security sources told Middle East News Agency (MENA) reported. The sources said that the joint forces are advancing towards Baiji's oil refinery, which is considered to be the largest oil refineries in Iraq, where the refinery's armed guards repelled Friday an IS attack, killing 29 militants. Moreover, the sources added that the coalition's air raids killed 23 IS militants in the northern city of Tikrit, Saladin province.