A National Police official said the detainees are accused of public disorder and damaging property, and remain in custody Monday.

This official said the riot police were only slightly injured. He spoke on condition of anonymity in line with department policy.

Madrid was one of several cities where tens of thousands of people rallied Sunday against austerity measures, what they see as incompetent, corrupt and pro-business politicians and a grim economic future in a country with 21.3 percent unemployment.