Libyan emergency services have been battling to contain a huge blaze at a major oil plant after it was targeted by unknown attackers.

The Zawiya refinery, west of the capital Tripoli, was hit in a drone strike on Monday evening - the third such incident in two days.

The National Oil Corporation (NOC) said a tank containing about 4.5m litres of fuel was directly hit, triggering a huge fire that caused it to collapse. It said it was considering suspending operations if the attacks continued.

There were no "serious injuries" from the fire, with most patients treated for smoke inhalation, Libya's Ambulance and Emergency Service said on Tuesday.

The Zawiya refinery is the largest operational facility in Libya, with an output of 120,000 barrels per day.

The NOC condemned similar attacks in past days in Zawiya, including two drone strikes on a naphtha reservoir and a water desalination plant.

It called on the authorities to investigate who was behind the violence.

The attacks have highlighted continuing instability in Libya, which has been split in two since a civil war broke out after the ousting of former leader Muammar Gaddafi.

Colonel Gaddafi seized power in 1969 and ruled autocratically for four decades until he was toppled and killed in 2011 in a rebellion assisted by Western military intervention

Since his fall, rival power centres, one based in the east backed by military commander Khalifa Haftar, and one in the west in Tripoli, led by Prime Minister Abdulhamid Dbeibah, have been jostling for political and military dominance.

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