German police step up manhunt after releasing Christmas market suspect

After releasing a Pakistani asylum-seeker arrested near the scene, authorities warned that the attacker is on the run and may be armed. They have also said it is unclear if the perpetrator was acting alone or with others.

Islamic State has claimed responsibility for the attack.

The head of the Association of German Criminal Detectives, told German television late on Tuesday that police hoped to make another arrest soon.

"I am relatively confident that we will perhaps tomorrow or in the near future be able to present a new suspect," Andre Schulz told a talk show on the ZDF public channel.

Wednesday's Passauer Neue Presse quoted the head of the group of interior ministers from Germany's 16 federal states, Klaus Bouillon, as saying tougher security measures were needed.

"We want to raise the police presence and strengthen the protection of Christmas markets. We will have more patrols. Officers will have machine guns. We want to make access to markets more difficult, with vehicles parked across them," Bouillon told the paper.

The 25-tonne truck smashed into wooden huts serving mulled wine and sausages, injuring about 45 people. Six of those killed were Germans and the Polish driver of the truck was found shot dead in the cabin of the vehicle.

German Chancellor Angela Merkel, who will run for a fourth term next year, said that it would be particularly repulsive if a refugee, seeking protection in Germany, was the perpetrator.

Some politicians have blamed her open-door migrant policy for making such attacks more likely.

The anti-immigrant Alternative for Germany (AfD), which has won support in the last two years as Merkel's own popularity has waned, said on Tuesday that Germany is no longer safe.

Some politicians have also called for changes to Merkel's immigration and security policies after she allowed more than a million migrants to enter Germany in the last two years, many fleeing war in the Middle East and Africa.

Bavarian Interior Minister Joachim Herrmann told German radio on Wednesday that there was a higher risk of Islamist attacks because of the influx of migrants.