Police foiled the alleged radical Islamist attack yesterday after conducting a pre-dawn raid on the couple's house in Oberursel and seized arms and ammunition from their residence, Police said.
"On the basis of the information we have at present, we have prevented a terrorist attack," Hesse's police commissioner Stefan Mueller said.
It is too early to establish the motives and the targets of the planned attack and the investigations are still continuing, he said.
Investigators found a pipe bomb, chemicals to make more explosive devices as well as arms and ammunition during the pre-dawn raid, police added.
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However, evidence collected during the raid and the contacts the suspects had with Salafists and other radical Muslim groups in Frankfurt pointed to an Islamist-motivated attack, Mueller told a news conference in the state capital of Wiesbaden.
Suspicions that the two may be planning to target Friday's cycle race "around the financial centres Eschborn-Frankfurt" have hardened after the main suspect was seen in the parking areas and the forests along the race track in the past few days.
This prompted the authorities to raid his house last night, Frankfurt's chief state prosecutor Albrecht Schreiber said.
The accused Turk has been known to police for his involvement in various offences, including robbery, cheating and illegal possession of weapons.
Police began monitoring the couple after they purchased large quantities of hydrogen peroxide from a supermarket in Frankfurt at the end of March under a fake name, Mueller said.