rtokens: The protest , which attracted several thousand supporters , coincided with the 18th anniversary of Spain 's constitution .
pos: NNS RB VBD CD NN ( CD NN ) IN NNS , NNS CC NN NN NNS .
tokens: Police also confiscated eight kg ( 18 lb ) of screws , balaclavas and spray paint cans .
ltokens: Hooded protesters threw burning bottles and other objects at police in Pamplona after the protest organised by Herri Batasuna , the political wing of Basque separatist group ETA .