"The death toll of the incident is now 73," state-run Radio Mocambique announced, citing authorities in Tete.
"The incident occurred when citizens tried to take petrol from a truck" in the village of Caphiridzange in Tete province, near Malawi, the government said in a statement yesterday.
The government added that 110 people were injured, some of them critically. Children were among the wounded, it said.
The precise circumstances of the explosion remained unclear.
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A local journalist told AFP the truck had crashed on Wednesday and exploded on yesterday afternoon, as scores of people tried to siphon off fuel.
The government "deplores the loss of life... And is currently providing the necessary assistance in order to save lives and to comfort the victims' families," it said.
Three ministers were due to arrive at the scene today in order to monitor the rescuers' work.
The government recently increased the price of fuel, after the value of the local currency -- named metical -- sunk against the dollar.
The southeast African nation is also undergoing a new political crisis, triggered by the former rebels' decision in 2013 to return to arms in order to push for a power-sharing deal with the government.
The current unrest has pitted the so-called RENAMO rebel force against government troops in the centre and the west of the country.
While many have returned, around 2,500 refugees from Mozambique still reside in Malawi, the UN refugee agency says.
Tete province was also hit by another tragedy in January 2015, when 75 people died from intoxication after drinking traditional beer.