German newspaper Die Welt quoted a senior police official as saying on Tuesday that they have arrested a wrong man suspected of the Christmas market attack, adding that the real perpetrator is armed and still at large
"As far as I know it is in fact uncertain whether that really was the driver," said Berlin Police President Klaus Kandt.
Berlin police said on Twitter that they were being vigilant as the suspect had denied involvement in the incident, which police have said was a deliberate attack.
"The temporary arrested suspect denies the offense. Therefore we are particularly alert. Please be also alert," Berlin police tweeted.
Earlier reports suggested that the man originally arrested was reported to be a 23-year-old Pakistani asylum seeker who arrived in Germany last year.
Security sources told local media he was not previously known to intelligence agencies as a potential Islamist.
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In the early hours of the morning, hundreds of armed police raided Germany's largest migrant accommodation centre at the disused Flughafen Tempelhof airport, where the initial suspect had reportedly been registered.
Berlin's public radio station RBB-Inforadio reported that the suspect was a Pakistani citizen who entered Germany on December 31, 2015, citing an unnamed security source.
News agency Deutsche Presse-Agentur (DPA), also citing unnamed security sources, reported that he came to Germany as a refugee in February 2016.
Berlin's Tagesspiegel newspaper reported that the man was known to police for minor crimes.
The recent attack was similar to an attack in Nice in July where 86 people were killed by a truck driven by a terrorist inspired by Islamic State of Iraq and the Levant (ISIL).