Tripoli.  A thick, black cloud of smoke has rippled across Tripoli’s usually blue summer sky for at least three days, after an estimated six million litres of fuel were set ablaze in the latest battle between rival militias.

The plume and scorching flames have been visible across Libya’s most populated city, as several fuel tanks were hit during clashes on Tuesday, the state-owned National Oil Corporation said in a statement. The burning tanks are located on the road to the airport, a motorway that has been one of the main fronts in the latest round of fighting between rival armed groups.

On Wednesday, the groups agreed to a temporary halt to the fighting. The ceasefire came the same day as Mohammed Sawan, the leader of the Muslim Brotherhood’s political arm in Libya, called the attacks "legitimate”. Before the ceasefire came into effect, firefighters and workers at the site had been trying to contain the flames, but with clashes continuing and bullets flying nearby, they were forced to move out and watch as the fire continued to devour the fuel. "We have been trying our best to keep the flames under control, but as long as the fighting continues it will be impossible,” Libya’s National Oil Corporation’s spokesman, Mohamed al-Harrari, said.

"We almost had the tanks that were hit under control, but because of the fighting another tank was hit, and the flames spread,” Harrari added.

The Libyan government released a statement requesting international assistance to help fight the fire, which threatens to cause a humanitarian and environmental catastrophe. The militias involved in the fighting are from two cities that once stood together against former Libyan leader Muammar Gaddafi in 2011. Islamist-led forces from Misrata initiated the attacks on July 13 against forces from Zintan, a small but powerful mountain town that pledged allegiance to an anti-Islamist former general, Khalifa Haftar, in May.