Authorities have searched the homes and workplaces of the two suspects accused of working for a foreign secret service. One of them, identified as Dieter S., had since October 2023 discussed possible plots with a person linked to the Russian secret service, prosecutors said.

Germany has become one of Kyiv’s biggest suppliers of military aid since Russia launched its full-scale invasion of Ukraine on Feb. 24, 2022, and is a major target for Russian spying operations, authorities have said.

“Our security authorities have prevented possible explosive attacks that were intended to target and undermine our military assistance to Ukraine,” Interior Minister Nancy Faeser said.

“It is a particularly serious case of alleged spy activity for (President Vladimir) Putin’s criminal regime.”

Dieter S. had been prepared to carry out bomb and arson attacks on military facilities, including those operated by U.S. forces, prosecutors said, adding that he took photos and videos of military transport and equipment.

According to Spiegel magazine, the facilities included the Grafenwoehr army base in the southern state of Bavaria where Ukrainian soldiers receive training to use U.S. Abrams tanks.

The Kremlin said it had no information about the arrests and the Russian embassy in Berlin said it had not been officially notified. The U.S. embassy did not immediately respond to a request for comment.

The prosecutors suspect Dieter S., whose last name has not been disclosed due to German privacy laws, was a fighter for Russian-backed forces in eastern Ukraine from Dec. 2014 to Sept. 2016 in the self-proclaimed Donetsk People’s Republic.

He is in possession of a firearm, prosecutors said.

In a separate case, prosecutors last month charged an officer in Germany’s military procurement agency with attempting to pass secret information to Russian intelligence.

News of Thursday’s arrests coincided with a surprise trip by German Economy Minister Robert Habeck to Ukraine.

Germany also issued an urgent appeal for countries to help shore up Ukraine’s air defences as Russian forces continue to pound Ukrainian cities and infrastructure.

“We will continue to provide massive support to Ukraine and will not allow ourselves to be intimidated,” Faeser said.

(Reporting by Andrey Sychev, Sabine Siebold and Alexander Ratz; Writing by Rachel More and Matthias Williams; Editing by Madeline Chambers and Gareth Jones)