Twenty-three people were killed and more than 130 injured when a fire broke out after a gas tanker exploded while unloading at a ceramics factory in the Sudanese capital Khartoum on Tuesday, the government said.

The blast at a factory in a northern suburb was so powerful it blew the tanker into a nearby lot, according to witnesses and a senior civil defence official.

Video footage showed people running and shouting for help at the site of the accident. Flames and smoke billowed from the factory as volunteers and security forces tried to put out the fire.

The fire completely destroyed the factory, a government statement said.

"I don't understand what happened, I heard a blast and ran. One man in a galabeya (a long flowing garment) was running behind me, he suffered a serious injury and I was also injured in my leg," said William, a factory employee.

"I pulled out 14 bodies which were completely burnt," said Hussein Omar, a volunteer at the scene.

The government called on citizens to donate blood to treat the wounded.

"Preliminary observations indicate a lack of necessary safety measures and equipment at the factory, in addition to random storage of flammable materials," the government statement said.

The casualties included employees of various nationalities, among them some from Asian countries, medical sources said.

Those injured were transferred to hospitals in the capital. Some were in critical condition, a local police chief said.