One of the suspected killers of Saudi journalist Jamal Khashoggi has been arrested at Roissy airport near Paris as he was about to board a flight to Riyadh, sources say, a move welcomed by his fiancee and a rights group as a potential breakthrough.

A police source named the man as Khaled Aedh Al-Otaibi, a former Royal Guard of Saudi Arabia.

A judicial source confirmed the arrest and said authorities were in the process of verifying his identity.

But a Saudi official said it was a case of mistaken identity, adding that those convicted of the crime were serving their sentence in Saudi Arabia.

Khashoggi’s fiancee Hatice Cengiz had earlier welcomed reports of the arrest, which came days after French President Emmanuel Macron held face-to-face talks in Saudi Arabia with de facto ruler Crown Prince Mohammed bin Salman.

“France should try him for his crime, or extradite him to a country able and willing to genuinely investigate and prosecute him as well as the person who gave the order to murder Jamal,” Ms Cengiz said.

Khashoggi, a critic of Prince Mohammed, was last seen entering the Saudi consulate in Istanbul on October 2, 2018.

Turkish officials believe his body was dismembered and removed. His remains have not been found.

Mr Al-Oaibi was arrested on the basis of a warrant issued by Turkey in 2019, the police source told Reuters, adding French prosecutors would begin proceedings for a potential extradition.

Mr Al-Oaibi, who is mentioned on British and US sanctions lists as being involved in Khashoggi’s murder, was also on a French wanted list.

“This could be a major breakthrough in the quest for justice for Jamal Khashoggi but more confirmation required,” said Agnes Callamard, head of Amnesty International who previously led a United Nations investigation into Khashoggi’s killing.

“If it is indeed the same person as that named by various sanctions lists and my report, then he was at the Consulate Residence at the time.”

RTL radio was the first to report news of Mr Al-Otaibi’s arrest earlier on Tuesday.

A Saudi official told Reuters there had been a mistake.

“Media reports suggesting that a person who was implicated in the crime against Saudi citizen Jamal Khashoggi has been arrested in France are false,” the Saudi official said.

“This is a case of mistaken identity. Those convicted of the crime are currently serving their sentences in Saudi Arabia.”

Last year, a Saudi court jailed eight people for between seven and 20 years over the killing but none of the defendants was named.

The trial was criticised by a UN official and human rights campaigners who said the masterminds of the murder remained free.

The French Interior Ministry and the Saudi embassy in Paris declined to comment.

-AAP