NEW : Oakland City Hall closes . NEW : Protesters vow to stand their ground at the DC camp . But none of the weekend activities rose to the level of violence witnessed in Oakland , where protesters on Saturday clashed with police after they were prevented from taking over a long-vacant auditorium in the heart of downtown . Mass arrests in Oakland among largest in city history , police say . Arrests are reported in New York , Chicago and Tampa .
NEW : Oakland City Hall closes . NEW : Protesters vow to stand their ground at the DC camp . Mass arrests in Oakland among largest in city history , police say . Arrests are reported in New York , Chicago and Tampa .