One day after a man drove a rental truck into a crowd of pedestrians gathered on Nice's waterfront promenade to watch the Bastille Day fireworks, no group has yet claimed responsibility for the attack.

Still, officials in France have been describing the attack, which has killed 84 and whose toll may rise, as terrorism. The driver was a 31-year old Tunisian man named Mohamed Lahouaiej Bouhlel, a not especially devout Muslim who had no known connections to religious extremism.

But President François Hollande immediately drew a clear parallel between the destruction in Nice on Thursday and the attacks that killed 147 people last year in Paris, the work of Muslim extremists. And Friday, Prime Minister Manuel Valls said the attack is the work of "a terrorist no doubt linked to radical Islam."

Nice, a picture-perfect resort town in the French Riviera, or Côte d'Azur in French, has become a known jihadist recruiting ground in the past few years. Authorities estimate that 55 people have left the area for Syria and Iraq since 2013. According to the prefecture, the Alpes-Maritimes department — of which Nice is the capital — supplies 10 percent of all French nationals who leave the country to wage jihad abroad. French jihad expert and RFI reporter David Thomson estimates that around 100 Nice residents are currently fighting alongside Islamist militant groups.

All that makes the Alpes-Maritimes one of the two biggest suppliers of French jihadists — the other being Seine-Saint-Denis, to the northeast of Paris.

As well as these known departures, authorities also know about 427 so-called radicalized individuals, making the area one of the three departments most affected by the phenomenon.

It is impossible to talk about radicalization in Nice without mentioning Franco-Senegalese jihadist Omar Diaby. Nicknamed "Omar Omsen," the 41-year-old recruiter is believed to have sent dozens of locals to Syria over the past few years. Omsen, who grew up in the working class Bon-Voyage neighborhood, started collecting petty offenses as a teen, and was in and out of prison many times.

Omsen first gained a following in 2012, after posting a series of propaganda videos on YouTube under the alias "19HH" — "19" for the number of terrorists involved in the 9/11 attacks, and "HH" to symbolize the Twin Towers.

Omsen — who faked his death in August 2015 so he could undergo surgery outside of Syria — is believed to be once more in Syria, where he leads a "katiba," a brigade of fighters, in the al-Nusra Front, the Syrian branch of al Qaeda. Many of the fighters in his unit are believed to hail from Nice.

Just down the road from Nice, the city of Cannes has also emerged as a base for would-be jihadists. From September 2012 to February 2014, French authorities carried out operations to dismantle the so-called Cannes-Torcy network, which had members in both Cannes and Torcy — a small town east of the capital Paris. Police arrested several members of the group, who were charged with plotting four terror attacks.

The most recent foiled attack was a plot to strike during the 2014 Nice carnival — a historical event that attracts several hundred thousand spectators each year. Three days before the start of carnival, authorities arrested a man on his way back from Syria who was planning to blow himself up in the parade.

In October 2014, 11 members of the same family —including several children — left Nice for Syria. Ivano Sovieri, whose daughter and two grandchildren were among those who left, told Nice Matin that his daughter had left a note to her friend, saying: "I wasn't meant to go, but with Allah watching, I was unable to backtrack."

Nice has also had to worry about returning jihadists. In January 2015, France Info reported on a 19-year-old from Nice who fought in Syria from December 2013 and June 2014 before coming home and turning himself in to the authorities. The young man's attorney claimed that his client had fought alongside 19 young men aged between 14 and 19 who hailed from the same apartment block in Nice.

In order to tackle the growing issue of radicalization and prevent further departures, the city has introduced a number of initiatives based on collaboration between teachers, psychologists and magistrates. While it may be too soon to gauge if they have worked, according to the Nice prefecture officials are aware of only one person leaving for Syria in the last year.

Follow Pierre Longeray on Twitter: @PLongeray