GERB is collecting signatures from MPs to call an emergency session of parliament and to demand the resignation of its speaker, Mihaela Dotsova. The party said on social media that it has 39 signatures so far and needs 80 for the demands.

The move follows an incident on Thursday involving journalist Sonya Koltukliyeva, on the pavement outside the headquarters of Progressive Bulgaria. She opened the door of Dotsova's car, and a guard from the National Protection Service (NSO) shoved her to the ground. Koltukliyeva fell, hit her head and dislocated a shoulder. The same day, deputy speaker Atanas Atanasov called on Dotsova to resign.

The background: Atanasov calls on Dotsova to resign after incident between NSO and journalist

"We find it unacceptable that Mihaela Dotsova, after the rough reaction of the NSO guards protecting her, calmly left the scene of the incident," GERB wrote. The party says her conduct does not befit the institution she represents.

"The speaker of the National Assembly cannot claim respect for the institution and represent it after yesterday," GERB added.

The party is asking all opposition groups in parliament to back both demands.

The NSO officer went to the Military Prosecutor's Office on his own and gave a statement. At about 1am, he was led out of the building in handcuffs.