An oil tanker explosion killed at least 27 people and injured 79 others in the impoverished northern Lebanese governorate of Akkar, the Health Ministry and Lebanese Red Cross said.
The explosion happened at a time of widespread fuel shortages, when much of the country is without electricity and long queues form at petrol stations.
Central Bank Governor Riad Salameh had announced a few days ago that fuel subsidies would be lifted.
The Lebanese Army has opened an investigation into the incident and President Michel Aoun summoned the Supreme Defence Council to discuss a response.
"At around 2am on Sunday, a fuel tanker that had been seized earlier by the army to distribute to the people exploded at an open area used for storing crushed stones in the village of Tleil in Akkar, leaving casualties among civilians and military personnel," the army said on its website.
It said it had arrested the son of the man who owned the land where the incident took place. The suspect was identified only by his initials in the army statement and his father's whereabouts were unknown.
A mob gathered at the man's home breaking windows and setting fire to his property. He is believed to have owned the fuel that exploded.
Hundreds of Akkar residents went to the site of the explosion and burnt the owner's lorry, the National News Agency reported.
Akkar governorate, on the border with Syria, is one of the poorest areas of Lebanon.
The explosion heaped more misery on a country struck by an economic crisis and severe fuel shortages that crippled hospitals and caused power cuts that last up to 22 hours a day.
Videos of the explosion seen on social media show a fire consuming metal scraps.
"Look at how the people are burning," a man can be heard saying in one video shared by a local news outlet.
"Our teams have transported 20 dead bodies ... from the fuel tanker explosion in #AKKAR to hospitals in the area," the Lebanese Red Cross said on Twitter.
Yassine Metlej, an employee at an Akkar hospital, said it received at least seven bodies and dozens of burn victims.
"The corpses are so charred that we can't identify them," he told AFP. "Some have lost their faces, others their arms."
He said the hospital had to turn away most of the injured because it was unable to treat severe burns.
Mohammad, an employee at a nearby hospital, said more than 30 injured people had arrived seeking treatment, but were turned away.
"They all have burns," he said.
They were turned away because the hospital is not equipped to treat them, Mohammad said.
Others were treated 25 kilometres away at Al Salam Hospital in the northern city of Tripoli, the only health centre in the region that can care for burn victims.
"The fear of losing fuel oil, medicines and supplies necessary to treat the injured is our concern now," Lebanon’s Health Minister Hamad Hassan said on Monday.
Electricity, fuel and medicine shortages have weighed heavily on Lebanese hospitals and impeded their ability to function normally.
Turkey took in on Sunday three patients with severe burns for treatment, while Kuwait sent 7.5 tonnes of medical aid to Lebanon.
Dire fuel shortage
Lebanon, hit by a financial crisis described by the World Bank as one of the worst since the 1850s, has been tackling soaring poverty, a plummeting currency and dire fuel shortages.
On Saturday, the Lebanese Army said it seized thousands of litres of petrol and diesel that distributors were stockpiling.
Fuel shortages have left many with only two hours of electricity a day, while several hospitals have recently given warning that they may have to close because of power cuts.
Mr Aoun has ordered security forces to pursue rescue operations and ensure the injured had access to urgent medical treatment.
Mr Aoun later told warned against politicizing the incident to create tensions.
"During the last session, I presented a report on the situation in the north, specifically activities undertaken by extremist groups to create chaos and security instability," Mr Aoun told the supreme defence council before the meeting started, urging security agencies to coordinate their efforts.
His remarks drew criticism from former prime minister Saad Hariri, who dismissed the president's claims about radical groups in the area and called on the latter to step down, blaming him for the economic crisis engulfing the country.
Earlier in the day, Hariri drew similarities between the Akkar and Beirut explosions.
"The Akkar massacre is not different from the port massacre," he said on Twitter.
"If this was a country that respects its people, its officials would resign, from the president to the very last person responsible for this neglect."
Prime minister-designate Najib Mikati said victims of the blast fell prey to those "who have exploited the fuel crisis to achieve illegal profits".
He vowed to crack down on the smuggling and illegal storage of fuel.
"It's a new black and bloody dawn in the history of Lebanon and the Lebanese people," Parliament Speaker Nabih Berri said in a statement carried by NNA.
He offered his condolences to the victims' families and the Lebanese Army, which reportedly lost several soldiers in the explosion.
Health Minister Hamad Hassan ordered hospitals to provide treatment for victims of the blast at the Health Ministry's expense while several countries pledged to dispatch medical aid.
Caretaker prime minister Hassan Diab said that Egypt, Turkey and Iraq have offered medical aid. Jordan also said it was sending assistance.
On August 4, 2020, a haphazardly stored stock of ammonium nitrate fertiliser exploded and left large parts of the capital looking like a war zone.
It was one of history's largest non-nuclear explosions.
In the year since, no officials have been held to account for that blast.
Despite a worsening economic crisis, political wrangling has delayed the formation of a new government after the last Cabinet resigned following the port explosion.
International donors have pledged hundreds of millions of dollars in humanitarian aid to Lebanon. But the money is conditional on the formation of a new government prepared to spearhead reforms, and on the resumption of talks with the International Monetary Fund.