According to a source close to the investigation, the target of the raids is Guillaume Pradoura, a former assistant to embattled EU lawmaker Maximilian Krah, of the far-right Alternative for Germany (AfD) party.
Pradoura -- who was expelled from France's National Rally over an anti-Semitic picture -- now works for the Dutch far-right lawmaker Marcel de Graaff.
The prosecutor's office said searches were being conducted at a staffer's home in Schaerbeek, northeast Brussels, and his offices in both Brussels and Strasbourg -- with cooperation from French authorities.
In a statement, it said the "searches are part of an investigation into interference, passive corruption and membership in a criminal organisation".
They "concern evidence of Russian interference, indicating that members of the European Parliament were approached and paid to promote Russian propaganda via the news site Voice of Europe," the prosecutor's office said.
"Evidence suggests that the European Parliament staffer in question played an important role in this case," it added.
Belgian prosecutors opened a probe last month into the meddling allegations, after Czech intelligence exposed a network suspected of using EU lawmakers to spread Kremlin propaganda.
The claims centred on Voice of Europe, which has since been banned under EU sanctions.
EU lawmakers face strict rules regarding independence and ethics, and can face penalties -- financial and otherwise -- if they violate them.
Belgium says its own intelligence has determined that some lawmakers were paid to promote Moscow's propaganda.
Pradoura's former boss Krah is himself being investigated for suspicious links to both Russia and China, and another of Krah's parliament aides was arrested on suspicion of spying for China.
The snowballing scandals surrounding Krah led his AfD party to be expelled last week from its group in the EU parliament, the far-right Identity and Democracy.
He remains the AfD's top candidate in the June 6-9 European election -- since it is too late to remove him from the position.
Join the conversation in our comments section below. Share your own views and experience and if you have a question or suggestion for our journalists then email us at [email protected].
Please keep comments civil, constructive and on topic – and make sure to read our terms of use before getting involved.
Please log in here to leave a comment.