The two suspects, identified as Halil and Senay D, were arrested overnight in Oberursel near Frankfurt, Die Welt newspaper reported Thursday.
While searching the suspects' apartment, police found a pipe bomb, explosives, a rifle and ammunition, as well as tools that can be used to detonate a bomb, the paper said on its webpage.
The suspects had been put under police surveillance several weeks ago, after buying unusually large quantities of chemicals of the type which other terror groups in Germany had previously used to make explosives. The couple reportedly used false names during the transaction.
Recently, Halil D. was observed surveying an area around Oberursel, near the path of a bicycle race scheduled for May 1. This prompted the police to arrest both him and his wife in order to avoid endangering participants and the audience, according to Die Welt.
The investigators also believe that Halil is connected to the al Qaeda terror network and Islamist groups in Frankfurt, the newspaper reported.
The police confirmed that the arrests have been made and that more places are being searched, but refused to comment on the background. A news conference is scheduled for later Thursday.
dj/sms (Reuters, AFP, dpa)