Police are looking for this man after an assault in Waikanae.

Wellington police are hunting for a man suspected of slashing a complete stranger in the forehead on the platform at Waikanae railway station.

The 31-year-old victim, who suffered a gash to his head, did not know his attacker, who ran off across State Highway 1 and may later have boarded a southbound train, police said on Wednesday.

"It appears a weapon was used in the assault and a 31-year-old man has received a gash to his forehead," Detective Senior Sergeant Grant Ferguson said. "It is very fortunate that we are not looking at a more serious outcome for the victim."

Police have issued an image of the man they believe to have been responsible for the attack, and have asked for the public's help in identifying and catching him.

"This brazen violence in a public place is of real concern to us, and we are committed to responding quickly to ensure the public's safety, and preventing further incidents," Ferguson said.

Anyone with information on the attack is urged to call Kapiti-Mana police on 04 296 6800 or Porirua police station on 04 238 1400. Alternatively, people can call Crimestoppers and provide information anonymously by phoning 0800 555 111.