Four people have been arrested in connection to an alleged politically motivated attack that has left a 18-year-old leftist dead in Paris, French authorities said.

Interior minister Manuel Valls said four individuals, including the one who probably struck the blow that killed Clement Meric, are being questioned by police.

The four - three men and a woman - are aged between 21 and 37 and have been identified thanks to photos and eyewitnesses' testimonies, police sources told AFP.

Meric, a member of an anti-fascist group, was beaten to death following a dispute between left-wingers and skinheads at a clothes sale in Paris central 9th district Wednesday evening, authorities said.

The politics student at Sciences Po University was attending a Fred Perry private sale in Rue de Caumartin with three friends, when four neo-Nazis sporting shaved heads and swastika tattoos arrived at the premises and an altercation erupted.

Meric was reportedly punched with a knuckle-duster and hit his head on the pavement.

Thursday morning he was declared brain dead by doctors at a Paris Pitié-Salpêtrière hospital, where he was taken in desperate conditions the previous evening. A few hours later, police confirmed Meric had died.

The deadly blow was delivered by a 21-year-old close to Paris-based neo-Nazi organisation JNR (Young Revolutionary Nationalists), police sources told the news agency.

JNR members were first accused of being behind the attack by far-left parties umbrella group Parti de Gauche that also urged lawmakers to ban violent far right organisations. JNR founder Serge Ayoub, 48, denied the allegations.

President Francois Hollande strongly condemned the attack and pledged swift action against far-right groups if the link between the attackers and organised political movement is confirmed.

"For too long these groups have created disorder and have to be repressed," Hollande said.

Hundreds of students gathered outside Sciences Po University to pay tribute to Meric.

UPDATE 7 June 2013: 24 hours after the arrest, French authorities reportedly released the female suspect. Another four people handed themselves into police in connection with the death of Clement Meric.

Sciences Po
Hundreds of students gathered outside Sciences Po University to pay tribute to Meric (Reuters)