BERLIN — Authorities in Germany on Wednesday arrested four suspected members of an Islamic State cell accused of plotting attacks on U.S. military bases in the country.

The Tajik nationals were detained in early morning raids in the western state of North Rhine-Westphalia, the public prosecutor said in a statement. A fifth suspected member of the cell, identified as Ravsan B., was arrested a year earlier, the statement said.

The details released by prosectors indicated that the plans were already underway: The cell had scouted U.S. Air Force bases in Germany and obtained firearms and ammunition.

Prosectors said Ravsan B. was in possession of instructions for the production of improvised explosive devices and had procured some of the necessary bomb-building materials online. He is also accused of agreeing to a contract killing in Albania for $40,000 to finance the plot, although the killing was not carried out.

German authorities did not release details of which U.S. air bases were targeted. Tens of thousands of U.S. troops are based in Germany, the biggest presence in any country other than Japan. Ramstein Air Base, in southwestern Germany, serves as the headquarters for the U.S. Air Force in Europe.

The suspects are accused of joining the Islamic State militant group in January 2019, having originally planned to travel to Tajikistan to carry out “jihad” before instead turning their sights to targets in Germany. The cell was in touch with senior Islamic State leaders in Syria and Afghanistan, according to German authorities, who said the group also funneled money to the cell through agents in Turkey.

The cell had also planned to kill an individual in Germany who had been publicly “critical of Islam,” the statement said. It added that one member of the cell had spied on the unidentified person.