Tanzania on Sunday laid to rest most of the 71 people who died while trying to collect leaking petrol from an overturned fuel tanker that exploded.

The deadly blast, which took place Saturday near the town of Morogoro, west of the economic capital Dar es Salaam, is the latest in a series of similar disasters in Africa.

President John Magufuli declared a period of mourning through Monday. He was represented at funerals by Prime Minister Kassim Majaliwa.

Mr Majaliwa spoke at a ceremony in Kola, less than 20 minutes from where the disaster occurred some 200 kilometres west of Dar es Salaam.

He gave a new death toll of 71, along with 59 injured.

White coffins were lowered into graves by members of the security forces, after which Islamic or Christian clerics said brief prayers and tossed handfuls of earth on them.

A Pentecostal pastor named Mechak said in a service broadcast on television that "this should serve as a lesson to us. When there is an accident like this we should steer clear and let rescue workers do their job."

DNA tests will be carried out on bodies that were burnt beyond recognition, Parliamentary Affairs Minister Jenista Mhagama said, adding that families could take the remains of their loved ones and organise their own burials if they preferred.

A woman who had accompanied her neighbour to retrieve the body of a victim at the hospital said: "When I saw the injured my whole body trembled. They had been burnt like pieces of meat."

Witnesses said the truck tipped over as it tried to avoid a motorcycle, and locals quickly converged on the scene to collect fuel.

The explosion was triggered when a man tried to retrieve the truck's battery, creating sparks that ignited the fuel, according to the region's governor.

Footage from the scene showed the truck engulfed in smoke and flames, with charred bodies and the burnt-out remains of motorcycle taxis scattered on the ground among scorched trees.

A video posted on social media taken before the explosion showed dozens of people carrying yellow jerricans around the truck.

"We arrived at the scene with two neighbors just after the truck was overturned. While some good Samaritans were trying to get the driver and the other two people out of the truck, others were jostling each other, equipped with jerricans, to collect petrol," teacher January Michael told AFP.

"At the same time, someone was trying to pull the battery out of the vehicle. We warned that the truck could explode at any moment but no one wanted to listen, so we went on our way, but we had barely turned on our heels when we heard the explosion."

President Magufuli on Sunday visited some of those injured in the blast at a hospital in Dar es Salaam.

"May God heal you," he said to the 43 patients, some in very serious condition.

Mr Majaliwa said Sunday that a special commission would investigate whether mismanagement had contributed to the disaster.

"While our now-dead compatriots were gathering to syphon fuel, did anyone try to stop them?" Mr Majaliwa asked.

Dr Magufuli has called for people to stop stealing fuel in such a way, a common event across Africa, saying he was "very shocked" by the dangerous practice.

Last month, 45 people were killed and more than 100 injured in central Nigeria when a petrol tanker crashed and then exploded as people tried to take the fuel.

In May, a similar incident occurred in Niger near the airport of the capital Niamey, leaving almost 80 people dead.

Among the deadliest such disasters, 292 people lost their lives in the eastern Democratic Republic of Congo in July 2010, and in September 2015 at least 203 people died the South Sudan town of Maridi.