Attacks raise fears in France

• A man died from a Monday attack in France, prosecutor says


• France adds another 200 to 300 security forces to patrol crowded areas


• The latest attack has not been linked to terrorism


• Two previous attacks allegedly involved people yelling "God is great" in Arabic

(CNN) -- One victim is dead and five others are hospitalized after the latest in a string of attacks that sparked fears in France, authorities said Tuesday.

Prime Minister Manuel Valls announced Tuesday the country is boosting security with up to 300 additional security forces.

A 25-year-old man died from his injuries suffered Monday night in Nantes, when a van plowed into shoppers at an outdoor Christmas market, Nantes prosecutor Brigitte Lamy said.

In addition to the five victims hospitalized, the driver is as well, Lamy said.

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The driver stabbed himself twice after the incident, but is expected to survive, said Pierre-Henry Brandet, a spokesman for France's Interior Ministry.

An investigation for murder and attempted murder has been opened.

Officials have said the incident appears to be an isolated case and not an act of terrorism. But it came after two other incidents in which the perpetrators were reported to have been yelling "God is great" in Arabic at the time of their attacks.

One took place Sunday in Dijon, in which a man rammed his vehicle into pedestrians, injuring at least 12, police said. A man has been arrested in connection with the case.

CNN affiliate BFM-TV reported that eyewitnesses heard the driver shout the phrase "Allahu Akbar."

On Saturday, a man stabbed three police officers in central France while allegedly calling out the same phrase. French counterterrorism authorities are investigating that attack.

CNN terrorism analyst Paul Cruickshank reported that the attacker behind Sunday's incident was a "40-year-old French-North African with a long history of psychiatric problems," and the perpetrator of Sunday's attack was a 20-year-old French-Burundian who had posted the ISIS flag on his Facebook page.

Police haven't revealed any possible motives.

France's Prime Minister has said his country has never faced as serious a terrorism threat as it does now.

"There is in France ... a terrorist threat," Valls said Tuesday.

"We want to protect and reassure the French and tell them that all state services are mobilized," Valls said, adding, "In these times of crisis, we must act with knowledge, judgment and self-control."

Crowded shopping and tourist areas are already being patrolled by about 780 soldiers, and those numbers were being by another 200 to 300 Tuesday, he said.

"We will not offer the victory of fear to those who want to weaken our democracy," the Prime Minister said.

European officials tell CNN the threat of terrorist attack in the European Union is greater than at any time since 9/11 because of the emergence of jihadist safe havens in Syria and Iraq, Cruickshank wrote for CNN.com. "But no country faces a greater terrorist threat than France, with support for ISIS running deep among disenfranchised immigrant communities in the rundown, crime-ridden banlieues (suburbs) that surround many French towns."