Legendary pharaoh Tutankhamun was probably killed by the genetic blood disorder sickle cell disease, German scientists said earlier this week, rejecting earlier research that suggested he died of malaria.

The team at the Bernhard Nocht Institute for Tropical Medicine in the northern city of Hamburg questioned the conclusions of a major Egyptian study released in February on the enigmatic boy-king's early demise.

That examination, involving DNA tests and computerised tomography (CT) scans on Tutankhamun's mummy, said he died of malaria after suffering a fall, putting to rest the theory that he was murdered.

But the German researchers said in a letter published online this week by the Journal of the American Medical Association that closer scrutiny of his foot bones pointed to sickle cell disease, in which red blood cells become dangerously misshaped.

"We question the reliability of the genetic data presented in this (the Egyptian) study and therefore the validity of the authors' conclusions," the letter said.

"(The) radiological signs are compatible with osteopathologic lesions seen in sickle cell disease (SCD), a hematological disorder that occurs at gene carrier rates of nine per cent to 22 per cent in inhabitants of Egyptian oases." Tutankhamun's death at about 19, after 10 years of rule between 1333 to 1324 BC, has long been a source of speculation.

One of the most common genetic disorders, sickle cell disease causes blood cells to take the shape of a crescent instead of being smooth and round, thereby blocking blood flow and leading to chronic pain, infections and tissue death.

The researchers called for further DNA tests on Tutankhamun's mummy for a definitive cause of death.