An elderly man's been seriously assaulted on one of Christchurch's popular walking tracks

Police say the man, aged in his 70s, was taking photos on Summit Road, at the top of the Rapaki Track on Saturday night, when he was approached and attacked by another man.

The offender is believed to have driven to the area - sometime between 11pm Saturday and 7 on Sunday morning - in a combi-style van and had two dogs with him.

The victim remains in hospital - being treated for serious head and facial injuries.