A picture taken on July 28, 2014 shows Libyan firefighters dousing a huge blaze at an oil tank started by clashes around Tripoli airport on July 28, 2014 in southern Tripoli. State-owned National Oil Corp has warned of a humanitarian and environmental catastrophe after the tank containing six million litres of fuel was set ablaze by rocket fire late on July 27, 2014. The Tripoli clashes, the most violent since the overthrow of dictator Moamer Kadhafi in 2011, started with a July 13 assault on the airport by a coalition of groups, mainly Islamists. AFP PHOTO / MOHAMED ELBOSIFI