French security agents arrested six people Tuesday on suspicion of plotting to attack French President Emmanuel Macron, according to a French judicial official.
Prosecutors have opened a preliminary investigation of alleged criminal terrorist association, the judicial official said.
The official, speaking on condition of anonymity to discuss the allegations, said intelligence agents detained the six suspects in three scattered regions: one in the Alps, another in Brittany and four near the Belgian border in Moselle.
The plan to target the French president appeared to be vague and unfinished, but violent, the official said.
Authorities said the six were between the ages of 22 and 62 and included one woman.
Interior Minister Christophe Castaner told reporters they are believed to be far-right activists. Authorities feared "concrete threats" from the group, Castaner said.
French presidents have been targeted several times over the decades. In 2002, a far-right sympathizer tried to attack President Jacques Chirac on the Champs-Elysees Avenue in Paris during Bastille Day celebrations.
Macron was in the northeastern French city of Verdun on Tuesday as part of centenary commemorations for the end of World War I.
The alleged plot was uncovered days before U.S. President Donald Trump and dozens of other world leaders are due in France for weekend observances marking the signing 100 years ago of the Nov. 11 armistice that ended World War I.