Berlin's airports remained on a high security alert on Tuesday just one day after the arrest of a terrorist suspect who security officials say was planning an attack on air transport hubs in the German capital.
The 22-year-old Syrian refugee, Jaber al-Bakr, was handed over to police on Monday morning by other Syrians, who had bound him with electric cable and held him in an apartment in the eastern German city of Leipzig after they realized he was wanted by the authorities.
Despite al-Bakr's arrest, security precautions at the Berlin's Tegel and Schoenefeld airports remained on a high level, police said.
Germany's domestic intelligence agency (BfV) head Hans-Georg Maassen told state broadcaster ARD on Monday they had received a tip last month that the Islamic State extremist group was planning an attack on German infrastructure.
"In the end the plan became more concrete to attack airports in Berlin," Maassen said.
In a separate case, the authorities said on Tuesday that a 28-year-old Syrian student living in the southern German city of Wuerzburg would remain in custody.
The medical student, whose name has not been released, was detained on Monday following what police said were allegations made by members of the public that he had made threats of a violent act against the state.
Police have so far declined to provide any details about the allegations about the student, including whether there was any concrete evidence of a terrorist plot or whether they found any explosives.
The investigation was still "at an initial stage," a spokesman for the prosecutor's office said.