Police have arrested two more people, one of them a 36-year-old man in a home for asylum seekers just 800 metres from the scene of the crime.
It remains unclear what role, if any, the man arrested in the asylum home is alleged to have played in the attack.
Responding to the attack, Friedrich Merz, the Christian Democrat opposition leader, said asylum seekers from Syria and Afghanistan should no longer be accepted in Germany.
“It’s not the knives that are the problem, but the people who walk around with them. In the majority of cases these are refugees, and in the majority of the crimes there are Islamist motives behind them,” he wrote in a decisive break with his predecessor Angela Merkel.
He added “Deportations can be made to Syria and Afghanistan, but we will not accept any more refugees from these countries.”
Germany debates asylum law and knife ban
In late May, a police officer was killed and five others injured by an Afghan national in an attack on an anti-Islam protest in Mannheim.
Since then Germany has been debating restrictions on immigration and asylum law as well as a ban on carrying knives, with Nancy Faeser, the interior minister, promising legislation would be delivered “soon.”
The German government had already opened up discussions with the Taliban in order to be able to deport rejected asylum seekers to Afghanistan.