PRISTINA- Masked assailants broke windows and threw a petrol bomb at the office of Kosovo's president on Saturday but failed to set fire to the building, police said.No one claimed responsibility for the 4 a.m. attack in the center of the capital Pristina, which the government condemned as "dangerous for the constitutional order and the country's stability.".Kosovo is facing a political crisis, with the opposition denouncing an EU-brokered deal with Serbia to give more rights to local Serbs. The issue is highly emotive, eight years after Kosovo declared independence from Belgrade and less than two decades after a war that drew in NATO."Masked people have hurled a petrol bomb at the president's office," the police said in a statement. "They broke the window with stones but failed to throw the petrol bomb inside and the bottle hit the wall."The office was empty at the time and no one was injured. Part of a wall facing a busy road was blackened by smoke from the burning petrol.Police were working to identify a white car they suspected was used by the assailants.