Strasbourg, France (CNN) A massive hunt is underway for a gunman who opened fire near a popular Christmas market in the center of the French city of Strasbourg Tuesday, killing three people and injuring 13 others.

More than 350 police gendarmes and soldiers supported by air units have been mobilized to find the suspect, who was already known to security services as a possible threat, police said.

Speaking to French radio station Inter on Wednesday, the county's Deputy Interior Minister, Laurent Nunez, said that authorities could not confirm that the suspect has "terrorist motivations."

Nunez added that while authorities have secured the border and set up a perimeter around Strasbourg, they are not sure if the suspect is still in France.

Nunez's comments come after the Paris Prosecutor's office confirmed to CNN that their anti-terror section was in charge of the investigation.

Strasbourg's famed Christmas Market is one of the oldest in Europe and draws millions of visitors each year. The suspect entered the perimeter of the market by the city's Corbeau Bridge, and began shooting at passers-by on the Rue des Orfèvres at 8 p.m. local time, when many were in the middle of their Christmas shopping.

Anti-terror police descended on the market and attempted to apprehend the suspect, who exchanged fire with security forces on at least two occasions between 8:20 p.m. and 9 p.m. French media reported the gunman was injured in one of the exchanges. He is then believed to have jumped into a taxi and fled the scene.

The attack prompted France to raise its national security threat level to its highest "emergency terror attack" status, French Interior Minister Christophe Castaner said at a press conference.

Eight people were seriously wounded, Strasbourg police said on Wednesday, with five others suffering from minor injuries.

Police secure a street and the surrounding area after a shooting in Strasbourg.

Gunman was known to police

The suspected gunman, who was identified by CNN affiliate BFM as a 29-year-old male born in Strasbourg, was on a French watch list called a "Fiche S" surveillance file.

The "Fiche S" is a French terror and radicalization watch list that includes thousands of people, some of whom are under active surveillance, meaning they are on law enforcement's radar.

The suspect was also "unfavorably known" by police authorities in France and Germany, Castaner told reporters on Wednesday, adding that he was known for non-terror related offenses.

French gendarmes had attempted to bring him in for questioning Tuesday morning before the attack but found he wasn't home, a spokesperson for France's National Police told CNN, without providing further details.

'People running, scared, crying kids'

Issam Fares, who sells chestnuts at the Strasbourg Christmas market, told AFP he heard several shots and thought they were fireworks "or they're attacking a store."

"I saw a lot of people running, scared, crying kids and all. Then I said, in my opinion it must be very, very serious, and then ... I saw people crying and the crowd leaving," he told AFP. "They said it was shooting right next door, so I ran away. I went to hide in a restaurant, not far from Gutenberg Street."

The injured were taken to a Strasbourg hospital.

Sur l'avenue de Colmar au Neudorf. Présence policière. Pas entendu de coup de feu. #strasbourg pic.twitter.com/vUL2CpMIkr — Allan Kilic (@AllanKilic) December 11, 2018

French President Emmanuel Macron tweeted early Wednesday in solidarity with the French people. "Solidarity of the whole Nation for Strasbourg, our victims and their families," he said

Terror attacks across Europe

The threat of terrorism has become a grim fact of life for parts of Europe, which has seen attacks on a Christmas market in the German capital Berlin in 2016, suicide bombings at Brussels Airport and a nearby Metro station that same year, and attacks on a busy downtown Barcelona avenue and a nearby Mediterranean beach resort last year, killing 13.

In the wake of the 2015 Paris attacks, French authorities launched a military operation called Opération Sentinelle -- in which 10,000 soldiers, police and gendarmes were deployed in Paris and its suburbs.

Strasbourg, a picturesque city of about 300,000 in France's Grand Est region on the border with Germany, has previously been at the center of French counter terrorism operations. The market itself was targeted 18 years ago in a thwarted plot by al Qaeda-linked terrorists.

In 2016, French authorities arrested seven people in anti-terror raids in Strasbourg and Marseilles. In 2012, police killed one suspect and arrested 10 others in the city as part of coordinated counter-terrorism operations.

Lockdown lifted

Following Tuesday's attack, the European Parliament in Strasbourg was placed on lockdown as the search for the gunman continued. Tweeting from inside, European Parliament President Antonio Tajani said that Parliament will "not be intimidated by terrorist or criminal attacks." He expressed "sorrow" for the victims, adding that Parliament will "continue to work and react strengthened by freedom and democracy against terrorist violence."

Containment measures were lifted hours later with police warning everyone to remain vigilant and follow safety instructions.

British Prime Minister Theresa May wrote on Twitter that she was "shocked and saddened" by the "terrible" attack in Strasbourg. "My thoughts are with all of those affected and with the French people," May tweeted.

The Christmas market will be closed Wednesday and flags will be at half-staff, Strasbourg Mayor Roland Ries said on his Twitter account. All shows scheduled to be performed at the city's cultural institutions will also be canceled on Wednesday, the mayor said.

The city's elementary, high schools and colleges will be open on Wednesday, local police said.

All rallies and demonstrations throughout the Strasbourg area were declared "forbidden" until further notice, the Prefecture of the Grand East and Lower Rhine Region said in a statement on Wednesday.