Suspected accomplice held in Vienna terror attack
Convicted Islamic State sympathiser Kujtim Fejzulai killed four people on the evening of November 2 before being shot dead by police in the first major attack in Austria for decades and the first blamed on a jihadist.
A spokeswoman for the Vienna prosecutors' department told AFP the arrested man was being investigated over a possible "contribution" to the attack.
Investigators were still looking into whether he was an active accomplice or simply knew of Fejzulai's plans, the spokeswoman said.
According to media reports, the 21-year-old Austrian national of Egyptian heritage was arrested on Friday at his parents' flat in one of Vienna's southern suburbs.
The attack was followed by a wave of arrests of people believed to be linked to Fejzulai, some of whom were subsequently released.
Prosecutors say that around 10 suspects are still in custody but that as yet no charges have been pressed.
At the time, Interior Minister Karl Nehammer said the police action was aimed at "cutting off the roots of political Islam".
The Styria region prosecutors' office said it was "carrying out investigations against more than 70 suspects and against several associations which are suspected of belonging to and supporting the terrorist Muslim Brotherhood and Hamas organisations".
It said "the operation has no connection to the terror attack in Vienna of November 2" but was the result of "intensive and comprehensive investigations carried out for more than a year".
Among the alleged offences are forming a terrorist association, financing of terrorism and money laundering.
The raids took place in the Styria, Carinthia, Lower Austria and Vienna regions.
"We are acting against these criminal, extremist and inhuman organisations with all our strength," Nehammer said in a statement.
The prosecutors' statement said the operation "was not targeted at Muslims or Islam as a religious community".
"On the contrary these measures are also intended to protect Muslims, whose religion is abused for the purposes of an ideology hostile to the constitution," it said.
Agencies contributed to this report.