A Hamilton dairy owner was left for dead in a pool of blood when three robbers burst into his shop and rained hammer blows to his head.

The 58-year-old was nursing his injuries when a delivery man discovered the horrific scene moments after the offenders fled.

"I asked him, please help me."

The man, who did not want to be named, was opening the Hillcrest Minimart in Cambridge Rd at 4.40am today when three young men rushed inside.

The man, a former South Korean soldier, stood up to confront the assailants and was bashed in the head with a hammer.

"They rushed through the door. They jumped up [onto the counter], and they carry some bags, and all of them carry a hammer.

"I was sitting here and I tried standing and he hit me. They tried to kill me."

As the robbers hastily grabbed at a tray of tobacco and cigarettes the man, determined to defend his property, jumped up and tried to lock the front door.

"I wanted to lock them in. Then they gave up and they pushed their way out, and then they disappear."

He said during his military service as a young man in South Korea he was selected to undertake further, specialised training.

However, he did not want to fight back in case he killed someone.

"If you kill them, then you have to go to jail."

During his conversation with the Herald the man bent over and picked up a clump of his hair from the shop floor.

His left eye was covered with a bandage and there was evidence of a gash on his scalp and blood spatter on his face and clothes. A female business partner cleaned the store as he spoke.

The dairy was robbed twice before in the past 18 months since the man and his business partner bought it, he said.

Those incidents, including the theft of his mobile phone from the shop counter two months ago, were minor with no injuries, until now.

"There's too much robbery, you know that. This is a big one. This is not New Zealand. This is ridiculous, unbelievable. I will sell [the shop] now."

The man came to New Zealand 20 years ago and said his children loved the country but he was now disappointed.

He said he could not give up selling tobacco because it was a large chunk of the dairy's income.

The former accountant said he believed this morning's robbers were teenagers, describing them as "skinny" but stronger than him.

When police arrived with a dog unit they established the offenders fled in a vehicle parked in a carpark nearby on Cambridge Rd.

The diary owner was taken to Waikato Hospital and treated head injuries and a significant eye injury.

A scene examination was conducted this morning and Senior Sergeant Charles Burgess said police wanted to speak to any witnesses on Cambridge Rd around 5am today.

This morning's robbery follows a spate of aggravated dairy robberies in the city during the past few months including a machete attack at a shop in nearby Hamilton East just three days earlier.

Call Hamilton police on 07 858 6200 or anonymously call Crimestoppers on 0800 555 111 if you have information.