France has detained and charged an 18-year-old man on suspicion of planning an imminent knife attack in the name of Islamic State (IS) jihadists, According to a judicial source,

Initial investigations revealed that he intended to carry out an attack “in the name of IS, to which he had pledged allegiance,” according to the unnamed source.

According to the source, the man was detained by France’s DGSI domestic intelligence agency in the Drome region of southeast France and indicted in Paris on charges of “terrorist conspiracy to prepare one or more attacks against people.”

“Thanks to the DGSI agents who were able to detain an individual who was planning an Islamist attack this weekend,” which begins with a Thursday bank holiday to mark the Ascension, a main Catholic feast day, Interior Minister Gerald Darmanin posted on Twitter.

The man, from a Muslim family, had become increasingly radicalized and was considered a threat, sparking France’s anti-terror prosecutors office to open an investigation on May 19, a source close to the case said.

Police arrested him on Friday and a video of him swearing allegiance to IS was found in his possession.

His statements in detention confirmed an attack was planned, most likely against random people in the street, the source said.

France has been on high alert since a wave of jihadist attacks began in 2015, killing over 250 people.

There has been no repeat of a mass atrocity such as the 2015 Paris terror attacks, which killed 130 people, but there have been several deadly attacks carried out by lone individuals.