BERLIN (Reuters) - Residents of Berlin warned on Tuesday against making hasty judgements about asylum-seekers after a 23-year-old Pakistani man was arrested in connection with a truck attack on a Christmas market that killed 12 people.

Flowers and posters are placed at the scene where a truck ploughed into a crowded Christmas market in the German capital last night in Berlin, Germany, December 20, 2016 REUTERS/Fabrizio Bensch

Oliver Horn, a German architect, put up a poster in French next to a pile of flowers near the attack site in West Berlin reading “Meme pas peur” (Not even scared!), a slogan that was used to show solidarity after the Paris attacks last year.

“We don’t have to be afraid. We just have to go on,” said Horn, standing near the Kaiser Wilhelm Memorial church, a Berlin landmark that was bombed to a jagged ruin in World War Two but left to stand as a monument to peace and reconciliation.

“I am afraid that people will become even more intolerant with this whole question of asylum-seekers in Germany,” he added.

Germany’s interior minister said the suspect, who denied involvement, was a migrant who had probably come from Pakistan and whose asylum application had not been completed. He was not in any database of known militant suspects.

But police later cast doubt on whether the arrested man was the attacker, saying it was possible the real perpetrator was still on the run.

Members of the anti-immigrant Alternative for Germany (AfD)party, which has seen its support rise following an influx of almost 900,000 migrants last year, were quick to blame the attack on Chancellor Angela Merkel’s asylum policy.

“I’m not saying that these deaths are Mrs Merkel’s fault but there are many hundreds of thousands of illegal immigrants in this country including many young men who are potentially violent,” Berlin AfD leader Georg Pazderski told reporters after signing a condolence book at the church near the attack.

Anselm Lange, head of the parish council at the Kaiser Wilhelm Memorial Church, warned against making rash judgements: “Peaceful coexistence is a delicate plant that needs to be looked after carefully, especially at difficult times like this.”

Foreigners make up almost 20 percent of the Berlin population of 3.6 million, with about 48,000 immigrants moving to the city in 2015, including 11,500 from Syria.

“As difficult as the situation is... Berlin couldn’t be Berlin without the peaceful cohabitation of people from all nations, all religions and all ways of life,” city mayor Michael Mueller told a news conference.

Among the candles and flowers, residents had placed signs showing their solidarity. One reading “Keep on living, Berliners!” was placed inside a picture of a Christmas tree. Another said: “I am Berlin, for more humanity and compassion.”

Pablo Ruiz, a teacher in the district of Neukoelln which has the highest percentage of immigrants in the city, had brought four of his teenage students to pay their respects.

“We wanted to show our sympathy, I wanted to show the students the importance of doing something, the importance of friendship and of co-operation,” he said.