A burning gas tank at the scene of a fire in Khartoum. AFP

Six of the wounded were in critical condition, Brigadier General Hassan Abdullah, northern Khartoum's Bahri district police director, told reporters.

The casualties include employees of various nationalities including some from Asian countries, medical sources said.

The fire came after a gas tanker exploded while unloading its shipment at the factory, witnesses said, adding that the blast was so powerful it blew the tanker into a nearby lot.

State TV said the blast had led to major loss of life and property, and that a rescue operation was ongoing.