A NEW Zealand teen has confessed to clubbing 23 fur seals - including newborn pups - to death with a galvanized steel pole on a beach in an attack which shocked the nation, The Marlborough Express reported.

The New Zealand fur seals, which are protected by law, were found slain late last year at a colony of the mammals about 22km north of Kaikoura, a township on the northeast coast of the South Island.

Jason Trevor Godsiff, 19, admitted charges of possessing an offensive weapon in a public place and willfully ill-treating 23 seals by clubbing them to death. He was remanded for sentencing in the Blenheim District Court in September.

A second man charged in connection with the same incident has not entered a plea.

Authorities believe the seals, some of which were just a few days old, were killed over several days. Some live animals in the area also had injuries.

Under New Zealand law the attackers face up to six months in jail, or a fine of NZ$250,000 ($199,064), for killing or harming fur seals, plus a fine of $10,000 per animal harmed.