A former EU diplomat is reportedly under investigation in Germany after being suspected to spy for China.
Two lobbyists are also involved, German media reported.
Police have raided homes and offices in Brussels, Berlin and other German towns in Baden-Württemberg and Bavaria. No arrests have been made so far.
One of the three suspects accused of espionage for China is a former German diplomat who has worked for the European Commission and the EU's External Action Service, where he represented the EU abroad.
Two suspects are accused of passing on information while a third is accused of considering to do so.
"There are allegations now and again of espionage taking place in Brussels by either Russia or China, but it's very unique that something this significant could actually come to the fold and be found out," Euronews' Shona Murray explains.
It is unclear how much information the suspects had access to. The investigation is ongoing.
This case comes at a very sensitive time for Brussels and Germany, as EU member states are considering whether to allow the Chinese tech company Huawei to develop 5G networks across the bloc.