A drunken Australian attacked a woman at random in a New Zealand city street, dragging her away and threatening to kill her before she escaped.

Security officer Shane Kenneth Boettcher told the 31-year-old woman, who was having trouble breathing as he held her: "Cooperate and you will live. Call for help and you will die."

Boettcher, 28, has no memory of the early morning attack on a woman walking to work in Christchurch, Christchurch District Court heard.

But although he says he was drunk, Boettcher accepted responsibility for what happened and was jailed after pleading guilty to charges of kidnapping and assault with intent to injure.

He was sentenced to two years and six months in jail, the Christchurch Court News website reported.

Defence counsel Gilbert Hay said Boettcher had no history of offending in Australia or New Zealand and could give no explanation for the attack.

Prosecutor Kathy Basire said the attack had a severe effect on the victim, who had nightmares and difficulty sleeping and could not go outside alone.

The court heard Boettcher had crossed the road to follow the woman and had put her in a headlock, lifting her up and dragging her towards a building.

She was held against a wall and her hair was pulled before a passer-by noticed what was going on, and she escaped.

Judge Stephen Erber said courts would not tolerate such behaviour, although he noted Boettcher's guilty plea meant his anxious victim did not have to give evidence in court.