French authorities have opened a case against Interpol president Ahmed Nasser al-Raisi of the United Arab Emirates over accusations of torture and arbitrary detention filed by two Britons who were detained in the country, a source close to the investigation said Wednesday.

The case into suspected complicity in torture by the top UAE official has been handed by French anti-terror prosecutors to an investigating magistrate who will now decide whether to press charges, the source, who asked not to be named, told AFP.

The two Britons, Matthew Hedges and Ali Issa Ahmad, accuse al-Raisi of having ultimate responsibility -- as a senior interior ministry security official -- for the torture and arbitrary detention they say they suffered in the UAE.

The source said the investigating magistrate must also decide if al-Raisi, who was elected Interpol president in November, enjoys diplomatic immunity from prosecution in France.

The Britons filed the complaint on the basis of universal jurisdiction, which allows states to prosecute serious crimes even if they were committed on foreign soil.

The opening of this case against al-Raisi goes a step further than the torture investigation opened against him by French prosecutors in November, over the detention of UAE dissident Ahmed Mansoor.

At the time, the UAE's foreign ministry rejected the complaints over Mansoor's detention conditions as "without foundation". 

In the latest case, the inquiry is now in the hands of an investigating magistrate, a step that precedes the pressing of any charges.

This means that al-Raisi could potentially be detained for questioning in France if his visits the country. Interpol's headquarters are in the southeastern French city of Lyon.

He is already believed to have visited Lyon several times since January.

The case was opened at the end of March, the source added.

Unfortunately the norm

Both plaintiffs were in Paris on Wednesday to testify before the investigating magistrate.

Hedges says he was detained and tortured in the UAE from May to November 2018 after being arrested on false charges of espionage during a study trip.

Sentenced to life imprisonment, he was eventually released after international pressure led by the UK.

Ahmad, meanwhile, says he was repeatedly beaten and even stabbed during a month in detention in January 2019, allegedly for enthusiastically supporting the UAE's Gulf rival Qatar in a football clash.

In a statement, Hedges said it was a "real moment of pride" to give evidence to the magistrate about the torture he says he suffered.

"Given the human rights record of the UAE it was incredible that al-Raisi was even elected as president. The torture that myself, Ali, and countless other people in the UAE have suffered is unfortunately the norm in the UAE," he said.

Ahmad said: "So many times I have lost hope that al-Raisi and all the other men that did this to me would get away with it with total impunity, but today is a good day."

Al-Raisi's four-year term at Interpol is largely ceremonial, with Secretary General Jurgen Stock handling day-to-day management of the organisation.

His candidacy for the Interpol job prompted an outcry from activists, who pointed to the generous funding Interpol receives from the United Arab Emirates.