A case of attempt to murder was registered against Taleigao MLA Anatasio Monserratte on Wednesday, police said.
The MLA, who was detained by Panaji police on Tuesday night was formally arrested along with CCP (Corporation of the City of Panaji) Mayor Tony Rodrigues.
Police have also detained Monseratte's wife Jennifer and son Amit after a mob, led by him, attacked Panaji police station last night.
Fifteen policemen were injured in the attack, officials said.
The mob, led by Monseratte, had gathered at the police station after two rival gangs from Taleigao clashed last evening, following which police arrested two persons acting upon a complaint.
The mob, demanding release of the two accused, turned violent when the police refused free the duo.