A series of dog attacks that have left three people injured, including a boy who was nearly killed, has prompted the RSPCA to renew calls for all dogs to be fitted with microchips.

An eight-year-old Rotorua boy was mauled by a bull mastiff and a German shepherd on Sunday morning.

Since then, a nine-year-old Blenheim boy, a Hamilton policeman and an animal control officer have also been attacked.

The Rotorua boy is in a stable condition in Waikato Hospital after needing more than 200 stitches for his wounds.

The bull mastiff was killed by police near Rotorua's Linton Park, where the attack took place. But they have been unable to find the German shepherd, despite Rotorua council staff spending hours sifting through a database of dog owners.

The boy's mother said her son had told her the German shepherd did the most damage.

She was at her son's hospital bedside on Monday.

"It was heartbreaking sitting with him there, he was just laying there ... I'm just dreading to see his legs. I haven't yet because they're all bandaged."

The dogs' owners could face a maximum penalty of three months' prison or a fine of up to $5000.

Auckland RSPCA executive director Bob Kerridge has called for all dogs to be fitted with a microchip so their owners can be readily identified.

"We'd know exactly whose dogs they were by now, and could take some action about it.

"We have to make sure it doesn't happen again. This is a way to make people accountable for their animals."

Mr Kerridge said the microchips, the size of a grain of rice, would cost about $20 each and could be implanted at registration. They would enable authorities to instantly track all details of a dog's owner.

Meanwhile, nine-year-old George Murray, of Blenheim, is recovering from a wound to his midriff after being attacked by a dog on Sunday.

He was playing rugby when he was bitten by a large rottweiler-cross. It grabbed his side and hung on for about 10 seconds.

Russell Montgomery, of the Marlborough District Council, said staff were treating the attack very seriously and wanted to find the dog as soon as possible.

In Hamilton, police constable Andy Boyd was attacked by a pitbull terrier as he served a summons notice in Pukete on Monday night. He was bitten on the legs.

A council animal control officer was also attacked.

The dog was removed from the property and put down.