A group of scientists has managed to establish the authenticity of a piece of cloth dipped in the blood of Louis XVI, France’s last king, after his execution during the French Revolution.

The monarch was executed by guillotine 220 years ago, becoming the first victim of the 'Reign of Terror.'

The discovery also proves the authenticity of a mummified head believed to be that of earlier French king Henri IV used in the DNA comparison, AFP reported.

According to a special tradition practiced during executions of France's elite, spectators were invited to dip their handkerchiefs in the gore of the decapitated victim as a 'souvenir.'

One such rag reportedly found its way into a calabash, a kind of squash dried and used as a bottle, on which was written: “On January 21, Maximilien Bourdaloue dipped his handkerchief in the blood of Louis XVI after his decapitation.”

The artifact has belonged to an Italian family for more than a century. However, its authenticity has not been proven until now.

In 2010, analysis of DNA samples taken from blood traces found inside the vegetable container had already revealed that it probably matched someone of Louis' description, but scientists could not prove it belonged to the beheaded king as they had no genetic material from any of his relatives.

A breakthrough arrived when scientists examined the alleged mummified head of 16th Century king Henri IV, AFP said.

One of France’s most popular monarchs, Henry IV was assassinated in 1610 at the age of 57.

After his mummified head was stolen during the revolution, it reportedly changed hands a number of times and was later sold at auction.

In the latest study, which was conducted by French and Italian experts, the team detected a rare genetic signature shared by the two men, despite being separated by seven generations.

"This study shows that [the remains] share a genetic heritage passed on through the paternal line,” forensic pathologist Philippe Charlier told AFP. “They have a direct link to one another through their fathers. One could say that there is absolutely no doubt any more.”

“It is about 250 times more likely that [Henri’s] head and [Louis’] blood are paternally related, than unrelated," said study co-author Carles Lalueza-Fox of the Institut de Biologia Evolutiva in Barcelona.

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