US president has dismissed allegations against Saudi Arabia as another case of 'guilty until proven innocent'.

The New Zealand Government has formally condemned the killing of journalist Jamal Khashoggi by Saudi operatives earlier this month, calling it "deeply disturbing".

Foreign Affairs Minister Winston Peters and Minister for Trade and Export Growth David Parker issued a joint statement on Sunday afternoon, saying the Government "continues to condemn in the strongest possible terms" the journalist's death.

The statement comes after Khashoggi disappeared while visiting the Saudi consulate in Istanbul on October 2. The Saudi government on Saturday admitted that the journalist was killed during the visit, saying he died during a fist fight.

Mark Tantrum/GETTY IMAGES Foreign Affairs Minister Winston Peters said many questions about the death remained unanswered.

"With the confirmation of the death we express our deepest condolences to Mr Khashoggi's family and friends. Those responsible for his death must be held accountable," said Peters.

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"While this is an important admission, the killing by government operatives is deeply disturbing. Many questions remain unanswered.

HASAN JAMALI/AP Saudi journalist Jamal Khashoggi speaks during a news conference in Manama, Bahrain.

"We look forward to the results of the investigation being led by Turkey and we urge Saudi Arabia to implement its undertaking to participate openly and transparently in that investigation," Peters said.

Saudi authorities have arrested 18 Saudi nationals and have dismissed several senior officials following an initial investigation of the Khashoggi case.

Ministry of Foreign Affairs and Trade (MFAT) officials met with the Saudi Embassy in Wellington on Tuesday to raise New Zealand's concerns over Khashoggi's disappearance, and "reiterated to the Saudi Embassy the need for the investigation to be full and transparent", the New Zealand Government statement said.

Parker said no New Zealand officials would attend the upcoming Future Investment Initiative conference in Riyadh.

"As for the trading relationship in the region, the FTA talks remain stalled pending the Gulf Co-operation Council resolving their dispute with Qatar, which we do not expected to be resolved in the near future," said Parker.

"And the widely criticised Saudi sheep deal was an arrangement made by the previous government with a private sector partner, not with the Saudi Government."

The Government was awaiting the outcome of the Turkish investigation and "keeping all options for next steps under review", the statement said.