Israel's Mossad provided intelligence leading to Germany's arrest on Sunday, of an Iranian man suspected of planning a mass casualty attack.
German police have taken into custody a 32-year-old Iranian citizen suspected of having procured deadly poisons cyanide and ricin to commit an "Islamist-motivated" attack, authorities in western Germany said on Sunday.
Israeli sources confirmed the Mossad's involvement after German Bild news paper reported a friendly nation's intelligence agency provided critical information.
The residence of the suspect in the city of Castrop-Rauxel was searched as part of the investigation, according to a joint press release from the Duesseldorf public prosecutor's office and police in the cities of Recklinghausen and Muenster.
"The suspect is suspected of having prepared a serious act of violence endangering the state by allegedly procuring cyanide and ricin to commit an Islamist-motivated attack," the statement said.
This, police said, carries a prison sentence of between 6 months to 10 years.
In Israel, security officials are conducting further investigations, probing if the Iranian suspect's was planning on harming Jewish or Israeli targets.
Castrop-Rauxel is located in North Rhine-Westphalia, Germany's most populous state, whose Interior Minister Herbert Reul said: "We had a serious tip-off that prompted the police to intervene during the night. The authorities are now investigating at full speed."
German police said a second individual was detained as part of the searches, adding a decision on whether to issue an official arrest warrant would be made at a later date as the investigation is continuing.
A spokesperson for the public prosecutor's office confirmed the person to be the suspect's brother.
Ricin, found naturally in castor beans, can cause death within 36 to 72 hours from exposure to an amount as small as a pinhead. No known antidote exists.
According to German domestic intelligence services, the number of members or supporters of Islamist causes has shrunk by 1.5% to 28,290 individuals in 2021, citing the "military breakup" of the militant Islamic State group.
On Dec. 19, 2016, Anis Amri, a failed Tunisian asylum seeker with Islamist links, drove a truck into a crowded western Berlin Christmas market, killing 11 people and injuring dozens.
News about Sunday's searches also comes a month after German authorities arrested 25 members and supporters of a far-right group that the prosecutor's office said was preparing a violent overthrow of the state.
Reuters contributed to this report