Police in Blenheim are cracking down on members of the Mongrel Mob after reports of two separate attacks at the weekend.
Inspector Steve Caldwell says the gang attacked party-goers at a house in Brewer Street on Saturday night after a female gate-crasher was ejected.
One man was hit on the head with a bottle, but was not badly hurt. Four Mongrel Mob members were arrested.
Mr Caldwell says two of the men were arrested again on Sunday morning after they returned to the house. They are accused of attacking people who were cleaning up.
Mr Caldwell says police action over the past year has halved Mongrel Mob membership in Marlborough to about a dozen.