The first CT scans to examine the king's mummy showed a cut to the neck deep enough to be fatal. The secret has been hidden for centuries by the bandages covering the it's throat that could not be removed for preservation's sake.
The work may end at least one of the controversies surrounding the Pharaoh's death, which has been long debated by the historians, the 'BBC News' reported.
Ancient documents including the Judicial Papyrus of Turin say that in 1155 BC, members of his harem attempted to kill him as part of a palace coup.
However, it is less clear whether the assassination was successful. Some accounts at the time imply the second Pharaoh of the 20th dynasty survived the attack.
Dr Albert Zink, a paleopathologist at the Institute for Mummies and the Iceman in Italy, and colleagues set out to examine the mummy of Ramesses III and the unidentified remains of another body found in a royal tomb near the Valley of the Kings in Egypt that was believed to be king's son Pentawere.
The team ran some CT scans and DNA tests on the mummies at the Egyptian Museum in Cairo where the bodies are now housed.
Also Read
Scans showed a deep, 2.7 inchs wide wound to the throat just under the larynx, which the scientists say was probably caused by a sharp blade and could have caused immediate death.
"Before now we knew more or less nothing about the destiny of Ramesses III. People had examined his body before and had done radiographs but they didn't notice any trauma. They did not have access to the CT scans that we do," Zink said.
"We were very surprised by what we found. We still cannot be sure that the cut killed him, but we think it did. It might have been made by the embalmers but this is very unlikely. I'm not aware of any other examples of this," said Zinka.
Researchers also saw a Horus eye amulet embedded in the wound - a charm most probably inserted by the ancient Egyptian embalmers during the mummification process to promote healing.
DNA tests also showed that the unidentified body of the young man, who was aged about 18 when he died, was a blood relative of Ramesses III, and in all probability the king's son Pentawere.