Russia announced on Monday the expulsion of at least 20 Czech diplomats in a furious response to the gutting of Moscow’s most critical intelligence station in central Europe over the weekend when Czech authorities accused Russian intelligence of being behind two blasts at an ammunition storage facility in 2014.

The Czech Republic has accused a notorious Russian intelligence unit implicated in multiple operations across Europe and the U.K. of conducting two operations in 2014 that led to explosions at a munitions factory in 2014. At the time, the ammunition was said to be headed for Russia’s rivals in Ukraine. After a nearly seven-year-long investigation into the blasts, Czech authorities detailed the links between the Russian intelligence agency GRU — including passports used in the 2018 Salisbury poisoning by suspected GRU agents — and began expelling Russian intelligence officers from Prague.

“Prague is a key station for [Russian intelligence] because it’s got a semi-friendly government and its central location inside the European Union makes it an excellent logistical hub for operations,” a central European intelligence official who tracks Russian operations in the area told Insider.

“The 18 ‘diplomats’ that were kicked out of [the Czech Republic] are well-known intelligence officials from [various Russian services] and were not just involved in operations targeting [the Czech Republic] but also targeting much of Europe,” said the official. “For operational purposes, I’m not sure there’s a more important EU station for the Russians outside of Berlin.”