Washington (AFP) - US Vice President Mike Pence vowed Tuesday to press Saudi Arabia for answers over journalist Jamal Khashoggi's "brutal murder" after Turkish President Recep Tayyip Erdogan 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 October 2, 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.

Pence, whose administration routinely criticizes 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.