The death toll has risen to 193 in South Sudan's fuel tanker explosion and the government has declared three days of mourning.

Patrick Raphael Zamoi, the governor of Western Equatoria state where the explosion happened Wednesday, said the death toll rose Saturday as more patients succumbed to their injuries.

Hundreds of people had gathered to scoop gasoline from a leaking truck which had veered into a ditch outside Maridi town when the tank exploded under unclear circumstances.

The Ministry of Health made an urgent public appeal for blood donations to treat injured patients who were evacuated to the capital, Juba, for better care.

Deadly fuel tanker explosions are common in East Africa, where poor residents living near highways converge around fuel tankers after accidents to steal gas.