AUCKLAND, New Zealand (AP) _ A man wielding a sledgehammer Friday badly damaged the America's Cup, international yachting's most prized trophy.

Police said that a man dressed in a suit walked into the Royal New Zealand Yacht Squadron clubhouse, where the cup is housed, and made his way unchallenged to a first floor room where the cup is kept on display in a glass case.

Police spokeswoman Joanne Gibbs said the suspect pulled out the sledgehammer and began striking the glass case in a frenzied attack.

The large ornate silver pitcher, which New Zealand took for the United States in 1995, was badly dented and scratched.

Royal New Zealand Yacht Squadron commodore John Heise said the man was was chanting in the ``Maori language.''

Witnesses said the man tried but failed to get the Cup out of the broken cabinet. The man tore off his jacket to reveal a protest-labeled T-shirt.

``He seems to have been a member of some protest group,'' Gibbs said.

Heise said the 3-foot-high silver cup was badly damaged around its mid-section.

``The Cup has been very, very badly beaten up,'' Heise said. ``He hit it a number of times with a big sledgehammer.''

The man was arrested minutes after the attack, but police did not immediately identify him.

Gibbs said the man arrived at the squadron rooms on the shores of Auckland Harbor about about 12:15 p.m. He walked by club officials and up a set of stairs, apparently with the sledgehammer hidden in his suit.

``The next thing they know he is smashing at the cabinet the cup is in,'' she said.

The suspect was slightly injured by broken glass from the cup cabinet.