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MAINZ, Germany — Three Syrian suspected ISIS members allegedly plotting a terror attack in Germany have been arrested, prosecutors said Thursday.

The men had received orders from ISIS leadership to attack the city of Duesseldorf using suicide vests, explosives and rifles — but that there was no concrete evidence they had begun to implement their plans, the prosecutors' office said in a statement.

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The trio were identified as 27-year old Hamza C., 25-year old Mahood B. and 31 year-old Abd Arahman A.K.

Officials were alerted to the plot when an alleged accomplice in French custody informed authorities there of the plans in February, according to the prosecutor's office.

It said German officials are seeking the extradition of the 25-year-old alleged accomplice — Syrian national identified as Saleh A. — from France.

That suspect — along with Hamza C. — allegedly joined ISIS in early 2014 and traveled to Turkey in May that year.

The prosecutor's statement said that by January 2015, the pair had convinced Mahood B. to participate in the attack. Saleh A. made contact with Abd Arahman A.K. a year later, the prosecutor added.

The arrests come after the head of the Germany's domestic intelligence service told NBC News last month that children as young as 13 were being brainwashed by ISIS and were "prepared to stage attacks" in the country.