STRASBOURG, France — A police operation was underway Thursday in the Strasbourg neighborhood where the suspected gunman in an attack near a popular Christmas market that killed three people last was seen.

One French police official said security forces, including the elite Raid squad, took action based on "supposition only" that the suspect, Cherif Chekatt, 29, could be hiding in a building nearby two days after the attack.

The official could not be identified because he was not authorized to disclose details on the investigation.

Authorities said a taxi driver dropped Chekatt off in the Neudorf neighborhood of Strasbourg on Tuesday evening after the shooting that also wounded 13 people. The suspect also was wounded while exchanging fire with security forces, officials said.

More than 700 officers have been searching Chekatt, who had a long criminal record and had been flagged for extremism, government spokesman Benjamin Griveaux told CNews television.

Asked about the instructions they received, Griveaux said the focus was catching the suspect "as soon as possible," dead or alive, and "put an end to the manhunt."

Chekatt allegedly shouted "God is great!" in Arabic and sprayed gunfire from a security zone near the Christmas market. Prosecutors have opened a terror investigation of the attack. Police distributed a photo of Chekatt, with the warning: "Individual dangerous, above all do not intervene."

The death toll rose to three Thursday with the death of a victim who was declared brain-dead earlier. Five of the people wounded were in serious condition, the prefecture of the Strasbourg region said.

France raised its three-stage threat index to the highest level and deployed 1,800 additional soldiers across France to help patrol streets and secure crowded events.

French authorities said that the suspect, born in Strasbourg, had run-ins with police starting at age 10 and his first conviction at age 13.

Chekatt had been convicted 27 times, mostly in France but also in Switzerland and Germany, for crimes including armed robbery. He had been flagged for extremism and was on a watch list.

French President Emmanuel Macron, speaking in Brussels where he is attending a European summit, said Interior minister Christophe Castaner would travel to Strasbourg on Thursday evening.

Griveaux called on the "yellow vest" protesters who have demonstrated across France since last month not to take to the streets. Some members of the movement planned a fifth round of demonstrations on Saturday across France to demand tax relief.

The usually busy streets of Strasbourg were eerily empty on Thursday morning, with a heavy police and military presence. The Christmas market was closed at least through Thursday, authorities said.

Some lit candles and brought flowers to a makeshift memorial at the site of the attack.

"You can feel a very heavy atmosphere due all these events," said resident Lucille Romance. "People are in a state of shock and are avoiding getting out of their house."

The dead included a Thai tourist, 45-year-old Anupong Suebsamarn, according to the Thai Foreign Ministry.

Italian Interior Minister Matteo Salvini said one Italian was among the wounded, in critical condition. The Europhonica radio consortium said Antonio Megalizzi, 28, was in Strasbourg to follow the session of the European Parliament.

Jean-Francois Badias in Strasbourg, Elaine Ganley in Paris, Colleen Barry in Milan, Italy and Raf Casert in Brussels, Belgium, contributed to this story.