Former head of Poland's internal security agency, Piotr Pogonowski, has been arrested in connection with the probe into the alleged abuse of Pegasus phone spyware.
Pogonowski was forcibly taken to testify before parliament after ignoring three summons.
Citizen Lab and Amnesty International found evidence of Pegasus spyware being used against critics of the previous Polish government.
The Polish senate deemed the use of Pegasus spyware in the country as unlawful.