Police have arrested two men with alleged links to the far right on suspicion of murdering Argentine rugby star Federico Aramburu, who was shot dead in Paris on Saturday.
The former rugby professional, who played for his national team as well as for several top-division clubs in Scotland and France, was fatally wounded in a drive-by shooting.
One suspect, a former soldier, had fled to Hungary and officers believe he was heading to Ukraine to fight against the Russians before he was apprehended. A second man was arrested in France.
Both men were linked with the extreme right, France's judicial office said.
In addition, a 24-year-old woman, who was arrested on Saturday, has been placed under investigation for alleged complicity.
Crime agency Eurojust said one of the suspects had fled to Hungary and was heading for Ukraine when he was detained by border police acting on a search warrant issued by French law enforcement authorities.
The French judicial official confirmed the man's identity as Loik Le Priol, who has alleged ties to banned extremist group GUD, which is known for violence. He allegedly created T-shirts that became a fad among far-right and identity groups in 2016.
The former marine commando, 27, was arrested at the Hungarian border post of Zahony, where he claimed "he was going to Ukraine to fight", Hungarian police said.
Officers said they found three knives in his car.
The French navy said Mr Le Priol had participated in French military operations in Mali and Djibouti but was repatriated in 2015 after a diagnosis of post-traumatic stress disorder and was later discharged because of violent behaviour.
The official confirmed that the other man, arrested in France's Sarthe region, was Romain Bouvier.
The two men were both allegedly members of the GUD white nationalist group.
Eurojust issued a European Arrest Warrant within an hour of Mr Le Priol's apprehension as Hungarian border authorities could hold him in preventive custody for only limited time before having to release him.
"The French and Hungarian desks at Eurojust were able to quickly transmit the EAW issued by the judicial authorities in Paris that same night and arrange the formal arrest of the suspect," Eurojust said.
"This now paves the way for a surrender of the suspect by the Hungarian authorities to France. Eurojust will enable the further assistance of this procedure."
France is now awaiting his deportation.
Aramburu was killed in Paris after a dispute in a bar.
The attack occurred in the chic Saint-Germain district on the Left Bank where Aramburu and some friends were having some food.
They group got into a heated argument with another group of patrons at the Mabillon bar before being separated by bouncers, but the other group later returned in a car and fired several shots, police said.
"There was an altercation, as there can be at the end of the evening. It was settled but the men came back and fired at Mr Aramburu, who took three bullets," said a former Biarritz Olympique player who was with Aramburu and asked to remain anonymous.
"Several bullet marks" were found at the scene, a source close to the investigation said, and Aramburu died as a result of his injuries.
Aramburu, 42, was a back who won 22 Argentina caps and played in the 2007 World Cup in France, scoring a try as the Pumas beat the hosts in the third-place play-off.
"This heinous crime and his death have left his family, friends and the world of rugby stunned and in unspeakable pain," a lawyer for Aramburu's family Yann Le Bras said.
Aramburu played club rugby in France for Biarritz, Perpignan and Dax from 2004 to 2010, winning the top 14 twice with Biarritz (BOPB) and later sitting on the club's board of directors.
Since his retirement from sport, he had lived in Biarritz and worked for a tourism company.
"We learn the death of Federico Martin Aramburu in tragic circumstances. The whole of the BOPB addresses its most sincere condolences to his family, his close relations, and assures them of its total support," the club tweeted.