A pressure group says Turkey's top administrative court has confirmed in a ruling that President Recep Tayyip Erdogan's 1,150-room mega-palace was illegally constructed on protected land.

Erdogan moved into the palace last year, brushing aside protests by opposition parties and advocacy groups who say the $620 million complex is unlawful.

The Ankara Chamber of Architects, which filed several cases against the palace, said Tuesday the Council of State has overturned a decision that allowed the construction of public buildings on some preserved sites. It says the ruling confirms the palace is illegal.

Court officials could not be reached and it was not clear what impact the ruling would have. Erdogan has dismissed previous court rulings saying: "Let them knock it down if they have the power."