A Christchurch pensioner savagely bashed by an armed intruder last night has been left scratching his bloody and sore head, wondering "Why me?"

The 70-year-old man, who asked not to be named, was at his Bamford St home in the Woolston area of the city when he thought he'd better make some tea at around 7pm.

"I'd left it a bit late so I thought, 'bugger it, I'll just have some soup'," he told the Herald today, his white hair stained red with blood and patched up with stitches and staples.

He went towards his kitchen pantry when his tiny bichon frise dog, Kokee, started barking at the back door.

The man, who lost his partner about a month ago, hadn't heard anything, and thought it was perhaps a cat.

When he went to open the back door, "it opened for me".

A masked man, dressed in dark clothing, was there and the senior citizen confronted him.

"I thought it was a practical joke, one of my nephews or son-in-law trying to scare the s*** out of me. Well, he scared s*** out of me all right," he said.

"He grabbed me [around the throat area] and started whacking me around the head."

He didn't see the weapon and doesn't know what it was – perhaps a rock or half a brick. "It was fricking hard."

Pushed inside, they crashed into the adjoining kitchen area where the attacker rained blows down on the man's head.

After about the fifth strike to the head area, the homeowner fell to the ground.

He lashed out with his feet.

"Whether I got him in the gonads or not, I'm not sure," he said, but his kicks resulted in the intruder fleeing back out the same door, chased by the dog.

Still conscious, the man phoned for an ambulance. The call-taker stayed on the line until police were first on the scene.

"There was blood for miles, all over the kitchen floor," he said.

The man was taken to hospital, where he received seven staples and four stitches to his nasty head wound before being discharged about 2.30am.

Today, he's wondering what the intruder's motive was, especially since nothing was taken.

"The biggest question is why? I have no idea why or who it was," the man said.

"Hey, I've got people I don't like but no enemies that I know of."

Shaken up, he might have someone stay with him for a while.

"You don't think that lightning will strike twice but who knows – I wasn't expecting that."

Detective Sergeant Brad Grainger described it as a serious assault and appealed for witnesses.

Anyone with information is urged to contact Christchurch Police on (03) 363 7400 or call Crimestoppers anonymously on 0800 555 111.