Firefighters try to extinguish a fire in one of the tanks at the Zahrani oil facility in southern Lebanon on October 11, 2021, sparking alarm as the country grapples with dire hydrocarbon shortages. AFP
There was no immediate report of casualties from the fire that sent large plumes of dark smoke billow into the sky.
The fire broke out around 8:00am (0500 GMT) in a large petrol tank belonging to the army at the Zahrani facilities some 50 kilometres (30 miles) south of Beirut, the National News Agency and local media said.
An AFP photographer said firefighters put out the flames at around noon (0900 GMT), and civil defence chief Raymond Khattar told the press the blaze was "under control".
Ziyad al-Zein, head of facilities at Zahrani, said the fire broke out as the tank was being emptied.
"We noticed an inclination in the reservoir's roof yesterday and took immediate measures... this morning to transfer its contents," he said, adding that "it would have been a disaster if the fire had spread to nearby tanks".
Energy Minister Walid Fayad said the flames had consumed around 250,000 litres of gasoline and that an investigation had been launched into the cause of the fire.
The army cordoned off the area, cutting off roads leading to the depot as well as the main highway linking Beirut to the country's south, the photographer said.
The Zahrani site also houses a power plant of the same name, and provides 15 percent of the country's fuel oil.
A worker in a plantation nearby told AFP he had heard a loud bang before the fire broke out.
The small Mediterranean nation is battling one of the world's worst economic crises since the 1850s, and has in recent months struggled to import enough fuel oil for its power plants.
In recent months, Lebanese have only received one or two hours of state electricity a day.
The fire comes after the electricity grid went completely offline on Saturday.
That outage came after two key power plants, including the one in Zahrani, ran out of fuel.
By Sunday limited supply was back after the army provided gas oil.
Most Lebanese saw no major change to their daily lives during the blackout, as those who can afford it have already subscribed to private generators to keep the lights on during the almost round-the-clock power cuts.
Petrol has also been in short supply, forcing motorists to queue for hours outside gas stations to fill up their tanks.