Former Argentina rugby player Federico Martin Aramburu was killed in Paris early on Saturday in a drive-by shooting after a dispute in a bar, sources close to the inquiry told AFP.
The attack occurred in the chic Saint-Germain district on the Left Bank where Aramburu and some friends were having burgers and about to call it a night at about 6am (0500 GMT).
They 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, one police source 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 Aramburu, who took three bullets," said a former Biarritz Olympique player who was with him and asked to remain anonymous.
"Several bullet marks" were found on the spot, said a source close to the investigation, and Aramburu died at the scene as a result of his injuries.
A murder investigation has been opened, the Paris prosecutor's office said, and the suspects were still being sought on Saturday.
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.
He 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 on Saturday.
A tribute will be held on Saturday night at the Stade de France stadium during the France-England clash, the last game of the 2022 Six Nations tournament, the French Rugby Federation said.
"What a nightmare, I'm still in shock and so sad for his family, his children, all his rugby friends from Biarritz, from Argentina," the former Stade Francais player and current deputy Paris mayor for sports, Pierre Rabadan, said on Twitter.
"On what is supposed to be a joyful day for French rugby, I have a heavy heart and a deep anger," he said.