A relative of one of the jihadist killers of journalists at French satirical magazine Charlie Hebdo has been arrested in Bulgaria after trying to get to Syria, a judicial source said Sunday.

Mourad Hamyd, brother-in-law of Cherif Kouachi who was behind the January 2015 attack in Paris that killed 12, was first detained in Turkey last month on suspicion of seeking to enter Syria, the source said. 

The 20-year-old student was then expelled to neighbouring Bulgaria, where he was sent to a detention centre on July 28, the source said, confirming a report in the Journal du Dimanche, a Sunday newspaper.

The source said French anti-terrorist investigators are preparing a European arrest warrant for Hamyd, who lived with his family in the northern French town of Charleville-Mezieres.

Hamyd's sister was Cherif Kouachi's wife. In the aftermath of the attack, Hamyd was  wrongly identified on social media as being one of three Charlie Hebdo killers.

He was held and questioned for 48 hours before being released without charge. Kouachi carried out the killings with his brother Said. 

Hamyd later told AFP in an interview he was shocked by the killings, which he described as "a horrible crime" and  described himself as a normal student living with his parents. He added he barely had any contact with Cherif Kouachi.

Bulgaria on Sunday confirmed the 20-year-old Hamyd's detention. 

"We did our job," Interior Minister Rumyana Bachvarova told AFP.

"He was detained and identified. All the necessary measures have been taken, he is not at large and we are awaiting the outcome of the judicial procedure" for his extradition, she said. 

A court could initiate extradition proceedings as early as Tuesday, Bachvarova said. She gave no details about where Hamyd was intercepted or being held.

According to a July tally by French Prime Minister Manuel Valls, France is home to more than 2,100 people -- French nationals or foreigners -- known to have links to Syrian and Iraqi Islamist groups.

Valls added that 203 of them who have spent time in those countries have returned to France.

SourcE: AFP