Investigators in Germany on Wednesday searched the homes of two men suspected of helping to plan last year's deadly terrorist attack in Vienna, federal prosecutors said.

Named as Kosovan Blinor S. and German Drilon G., the pair are accused of meeting the attacker through the radical Islamist scene and knowing about the planned rampage but failing to report it.

On November 2, 2020, convicted Islamic State sympathiser Kujtim Fejzulai killed four people in the Austrian capital before being shot dead by police.

It was the first major attack in Austria in decades and the first blamed on a jihadist.

Blinor S. and Drilon G. had been "in close contact with (Fejzulai) via social media for some time before the attack", prosecutors said.

The suspects, who live in Osnabrueck and Kassel, are accused of travelling to Vienna to visit Fejzulai for several days in July 2020, shortly after he procured the automatic rifle used in the rampage.

They stayed overnight in his flat and met other members of the Islamist scene from Austria and Switzerland, the prosecutors said.

DNA from participants in these meetings has since been found on the weapons used in the attack, as well as on the ring worn by the attacker.

It is likely the pair knew Fejzulai was planning the attack "due to their close personal relationship" with him and "their common radical Islamist convictions", the prosecutors said.

The two men are also accused of trying to conceal their connections to Fejzulai by deleting mobile phone chats and social media content on the evening of November 2, 2020, shortly before the attack.