Cap-Haitien (Haiti): With fuel in short supply all across Haiti, some neighbours in the northern city of Cap-Haitien saw the crash of a tanker truck as a chance to scoop up valuable spilled gasoline. But then the truck exploded, unleashing a fireball that swept across people and homes, and local officials say at least 75 people died.

Early reports indicate that the tanker was trying to avoid an oncoming motorcycle when it veered and flipped early Tuesday.

Onlookers then rushed to the scene with buckets to collect what they could of the tanker's cargo, likely for sale on the black market, as the fuel drained toward a nearby pile of smouldering trash.

"It was after midnight and I heard a loud noise so I asked one of my boys to go and look. He told me a gasoline truck exploded," said Abraham Joanis, 61, as he carried a guitar rescued from the charred remains of his home, one of about 50 gutted by the blaze.

Hours after the blast, buildings and overturned vehicles were still smoking as firefighters covered burned bodies in white sheets and loaded them onto the back of a construction truck.

"It's horrible what happened," said Patrick Almonor, deputy mayor of Cap-Haitien, the country's second-largest city, who said late Tuesday that 75 people had died.

Burn victims screamed in agony as they pleaded for help at Justinian University Hospital, the city's largest.

Prime Minister Ariel Henry, himself a physician, visited there as victims bandaged head to toe were fighting for their lives amid a shortage of medical supplies and health workers in an impoverished nation that has been bombarded by disasters in recent months riots, a wave of kidnappings, a powerful earthquake that killed more than 2,200 people and the July 7 assassination of the president.

Among survivors who spoke with the prime minister was Riche Joseph, who spent hours on the hospital's floor connected to an IV while he waited for a bed.

His sister, Bruna Lourdes, said her brother stepped out of the house late at night to look for something to eat. When she heard the explosion, she rushed down from the hillside shantytown in panic.

"I'm praying to God that he won't take his life," said Lourdes, who is studying to be a nurse and planned to spend the night by her brother's side to offer whatever assistance she can to the overstretched medical staff.

Henry, wearing a biohazard suit, clasped his hands and leaned over to console one man collapsed on the hospital's concrete floor because there were not enough beds in the historic city's largest hospital.

The prime minister promised more help in the form of field hospitals and a contingent of medical professionals. But minutes after he left the facility, five more patients died.

The entire Haitian nation is grieving," Henry said on Twitter while declaring three days of national mourning. "It is with a torn heart that I see the critical condition of some of our compatriots admitted to this facility."

At least 15 victims were evacuated by air to hospitals in the capital, Port-au-Prince.

Haitians for months have been scrambling to find gasoline amid shortages that have shuttered gas stations, sent fuel prices sprialling on the black market and forced businesses to close.

The country of more than 11 million people also has been hit by a spike in gang-related kidnappings, including 17 people with a US missionary organization who were abducted in mid-October.

Five of them have been released but another 12 are still being held.

"It's terrible what our country has to go through," said Dave Larose, a civil engineer who works in Cap-Haitien.