The FSB security service said on Tuesday that it had detained a group of former defense industry workers who allegedly provided Ukraine with sensitive military information and plotted sabotage attacks.

The anonymous former workers were accused by the FSB of spying for Ukrainian military intelligence and sharing crucial information, technical documents and models for making weapons systems and equipment for Russia’s Air Force.

The FSB said in a statement that the group also plotted to blow up the railway lines in Kursk and Belgorod regions that supply equipment to the Russian forces in Ukraine.

The ex-workers were charged with state treason and preparing sabotage acts and were detained and confessed, Reuters reported the FSB as saying. “More than four kg of plastic explosives, four detonators, military design documentation and goods for military purposes, as well as $150,000, have been seized,” it said.

Russia’s overnight missile attack on the central Ukrainian city of Kryvyi Rih killed at least 10 and injured 28 others. “One is under the rubble, 28 are injured,” Oleksandr Vilkul, the city’s military administration head, said on social media.