BERLIN/DUESSELDORF, Germany (Reuters) - The Tunisian man who killed 12 people last month by plowing a truck into a Berlin Christmas market had lived under at least 14 different names in Germany, a regional police chief said on Thursday, raising more questions about security lapses.

Anis Amri, the Tunisian suspect of the Berlin Christmas market attack, is seen in this photo taken from security cameras at Brussels North train station, Belgium, December 21, 2016. Federal Public Prosecutor's Office/Handout via Reuters

Anis Amri, shot dead by Italian police in Milan on Dec. 23, had been marked as a potential threat by authorities in the western federal state of North Rhine-Westphalia (NRW)in February 2016, some six months after he arrived in Germany and applied for asylum.

“He acted in a conspiratorial manner and used various personalities,” Dieter Schuermann, head of the NRW Criminal Police Unit, told the regional parliament during a briefing.

The 24-year-old divided his time between NRW and Berlin, where intelligence officials also classified him as a potential threat. But there was a consensus among security officials that he posed no concrete threat, Schuermann said.

An investigation into the attack is focusing on whether Amri had any accomplices.

Police arrested another Tunisian man in Berlin this week, who prosecutors say had dinner with Amri at an Arab restaurant in the capital one day before the attack on Dec. 19.

“INTENSIVE DISCUSSIONS”

A spokeswoman for the prosecution said on Wednesday that Amri and the arrested suspect, identified as 26-year-old Bilel A., had “very intensive discussions” at the restaurant on the eve of the attack.

The co-owner of the restaurant in north Berlin where the two allegedly met told Reuters on Thursday he had not been aware that Amri had dined at the premises until police came asking if they could have CCTV footage recorded on Dec. 18.

“No one who was here that night remembers seeing him,” said the co-owner, declining to give his name and requesting the eatery not be named.

“We are so busy we hardly have time to breathe. The police said he was here between 8 and 9 p.m.,” said the man, serving lunch as the restaurant began filling up.

At a shelter for migrants at the western end of Berlin where Bilel A. was arrested, refugees who said they knew Amri’s suspected accomplice said he had always told them he was Libyan.

“The strangest thing about him was that he used to pray every day but most evenings he would go out to nightclubs with his friends,” said Mohammad, a 21-year-old Syrian refugee who said he had shared a room at the shelter with Bilel A. six months ago before moving to another room at the facility.