Two German-Russian men have been arrested in Germany on suspicion of espionage, one of them accused of agreeing to carry out attacks on potential targets including U.S. military facilities in hopes of sabotaging aid for Ukraine, prosecutors said Thursday.

The two, identified only as Dieter S. and Alexander J. in line with German privacy rules, were arrested Wednesday in the Bavarian city of Bayreuth, federal prosecutors said.

Prosecutors allege Dieter S. had been discussing possible acts of sabotage in Germany with a person linked to Russian intelligence since October, and that the main aim was to undermine military support given by Germany to Ukraine.

The suspect declared himself willing to carry out bombing and arson attacks on infrastructure used by the military and industrial sites in Germany, prosecutors said in a statement. They added that he gathered information on potential targets, including U.S. military facilities.

Alexander J. allegedly helped him to do so starting in March at the latest, while Dieter S. scouted out some of the sites, took photos and videos of military goods and passed the information to his intelligence contact.

A judge on Wednesday ordered Dieter S. kept in custody pending a possible indictment, and Alexander J. was ordered held on Thursday.

Dieter S. also faces separate accusations of belonging to an armed unit of pro-Russian separatist forces in the Donetsk region of eastern Ukraine between December 2014 and September 2016.

Germany has become the second-biggest supplier of weapons to Ukraine after the United States since Russia started its full-scale invasion of Ukraine more than two years ago. The U.S. has a large military presence in Germany, including in Bavaria.

Prosecutors did not name any specific locations in the suspects’ sights. German news agency dpa and magazine Der Spiegel reported, without citing sources, that the locations allegedly snooped on include the U.S. Grafenwoehr military base.

Germany’s top security official, Interior Minister Nancy Faeser, said Russia’s ambassador was summoned to the Foreign Ministry in Berlin.

She vowed that Germany will continue to thwart any such Russian threats. “We will continue to give Ukraine massive support and will not let ourselves be intimidated,” she said.

Faeser wouldn’t comment on details of the investigation. She said that Germany has increased its security measures since Russia sent its troops into Ukraine in 2022 and will keep evaluating them.

Kremlin spokesman Dmitry Peskov said he couldn’t comment on the reported arrests, saying that he doesn’t have “any information on this matter.”

European officials have recently warned of Russia-linked interference networks trying to undermine European support for Ukraine in its war against Russia.

(AP)