"Investigators from the prosecutor's office showed up unannounced at the data center where Fidesz servers are located, with the aim of seizing the party's entire communication system and databases," the party writes.
The authority told the AFP news agency that it is investigating a criminal case in the county where the data center is located, including embezzlement, without providing any further details "because it would harm the ongoing investigation."
The country's new Prime Minister Péter Magyar has promised to hold those who enabled corruption accountable and to turn the page after 16 years of Orbán's rule.
Magyar says he first learned about the raid through the Facebook post.
