A man China wants extradited over the murder of a prostitute is "hyping up" his right to a fair trial to evade justice, says a top Chinese government official.

Amnesty International is urging the Justice Minister not to extradite New Zealand man Kyung Yup Kim to China for fears he will be tortured.

Korean-born Mr Kim faces murder charges after the beaten and strangled body of a 20-year-old sex worker was found dumped in wasteland in 2009.

He had been in Shanghai at the time visiting his girlfriend, but returned to New Zealand in 2010.


China sought his extradition the following year.

Mr Kim has been held in Mt Eden Prison for the past five years fighting any move to face charges that he denies.

Mr Kim's legal team challenged the extradition, arguing the minister hadn't properly taken into account the prevalence of endemic torture in China and assurances offered over the likely use of a death penalty.

New Zealand last December agreed to extradite him to face trial, but this week the High Court decided China's assurances of fair treatment for Mr Kim were inadequate.

Chinese officials said the Korean murder suspect was creating a smokescreen.

"Kyung Yup Kim and his lawyers have hyped up the issue of an impartial trial," Chinese Foreign Ministry spokesman Hong Lei said.

"In reality, it's for the purpose of evading legal sanctions."

He said China would continue to work with New Zealand authorities on the case to "crack down on lawbreaking".

Amnesty International executive director Grant Bayldon said people in China were treated as guilty before innocent and once convicted faced forced labour and prolonged torture which went against everything New Zealand stood for.

It would be a breach of New Zealand values if Mr Kim was extradited to China and there was a reason very few countries have extradition treaties with the country, he said.

"We've been monitoring the Chinese justice system for decades and what's absolutely crystal clear is that there are no assurances that could get past the fact that the Chinese justice system is fundamentally unjust."

New Zealand Justice Minister Amy Adams said the Chinese government had assured her Mr Kim would get a fair trial and not face the death penalty but the latest judgement said she failed to explicitly address why she's satisfied assurances to protect Mr Kim should be relied upon.

The court ruled Ms Adams must reconsider aspects of her decision.

Yesterday she said she was seeking advice on whether to reconsider her decision or appeal the latest ruling.