Key Points:

Christchurch police are seeking information on two men following a "cowardly and unprovoked" attack on a teenager with a claw hammer.

Senior Constable Keith Olds said that last Friday about 10.15pm near Blighs and Windermere Roads two men approached a group of four 16 and 17-year-old boys and demanded their wallets.

When the group said they had nothing to hand over one was attacked on his head with a claw hammer and required hospital treatment.

The offenders then ran down Tillman Avenue and through Waimairi School, Mr Olds said.

As they ran over the bridge that crosses the railway line they met another group of four young men who they threatened with the claw hammers but did not attack.

The offenders took their wallets and ran off down Hartley Ave towards Northcote Road.

One offender was described as male, probably Maori, 17-20-years-old, 1.82m, tall, slim build, with straightish, straggly, shoulder length hair.

He was said to be unshaven with "bum fluff" on his face. He was wearing a black T-shirt with a heavy metal band on it, under a blue checked "farm" type shirt.

The other was a male Caucasian, 17 to 19-years-old, 1.77m, average build with straight black/brown hair under a beanie.

He was wearing a red short sleeved T-shirt with a band name on it. His hammer had pink around the metal towards the head.

Mr Olds said any information would be treated as confidential. He can be contacted on (03) 374 1715.