US to 'demand answers' from Riyadh for Khashoggi murder: Pence

US Vice President Mike Pence vowed to press Saudi Arabia for answers over journalist Jamal Khashoggi's "brutal murder" after Turkish President Recep Tayyip Erdogan on Tuesday said the killing inside the kingdom's Istanbul consulate was meticulously planned.

"The world is watching. The American people want answers and we will demand that those answers are forthcoming," Pence told an event at The Washington Post, where Khashoggi was a contributing opinion writer.

Erdogan, in his most extensive public remarks since Khashoggi's disappearance upon entering the consulate on 2 October, called on Saudi Arabia to extradite suspects to Turkey to face justice over the writer's death.

"The word from President Erdogan this morning that this brutal murder was premeditated, pre-planned days in advance flies in the face of earlier assertions that had been made by the Saudi regime," Pence said.

"It underscores the determination of our administration to find out what happened," he said.

The strongly worded remarks come after days of mixed messages by President Donald Trump, who has vowed punishment but also ruled out major actions such as stopping arms sales to Saudi Arabia, a longstanding US ally.

Khashoggi, who lived in the United States and wrote critically about the Saudi royal family, died earlier this month at the Saudi Consulate in Istanbul. Saudi Arabia said he was killed in a fist fight, but Turkish officials said the 59-year-old journalist was attacked and killed by a 15-man Saudi team.

On Monday, Trump said he's not satisfied with the explanations he's heard about the death of Saudi writer Jamal Khashoggi and is awaiting reports from US personnel returning from the region.

Pence, whose administration routinely criticises the media, called Khashoggi's death "an assault on a free and independent press, and our administration is determined to use all means at our disposal to get to the bottom of it".

"We're going to demand that those responsible are held accountable and once we have all the facts President Trump will make the decision based upon the values of the American people and our vital national interests," he said.

The saga has provoked outrage across the globe, tarnishing Saudi Crown Prince Mohammed bin Salman's hard-fought image as a "reformer", and threatening to damage the kingdom's close ties with the US and Europe.

Several high-profile sponsors and speakers withdrew from a top economic summit in Riyadh this week, including the leaders of the World Bank and the International Monetary Fund, as well as JP Morgan, Uber and Ford.

Major Western media outlets including Bloomberg, CNN, the Financial Times and The Economist also pulled out of covering the summit.

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