International Monetary Fund chief Christine Lagarde has postponed a planned trip to the Middle East with a stop in Saudi Arabia for an investment conference, after a prominent journalist's disappearance.

"The Managing Director's previously scheduled trip to the Middle East region is being deferred," an IMF spokesman said in a statement, without further explanation.

Lagarde had been set to participate in the kingdom's Future Investment Initiative conference that has been boycotted by global business and media leaders since the suspected death of Jamal Khashoggi, who was last seen at the Saudi consulate in Istanbul on October 2.

On Saturday, during the IMF's annual meetings in Bali, Lagarde had said she would travel to Riyadh for the gathering next week.

"Human rights, freedom of information are essential rights and horrifying things have been reported and I am horrified," she told reporters at the time.

"But I have to conduct the business of the IMF in all corners in the world and with many governments.

"When I visit a country, I always speak my mind... So at this point of time my intention is to not change my plans and to be very attentive to the information that is coming out in the next few days."

But there have since been growing accusations against top levels of the conservative kingdom over the Khashoggi case, triggering a diplomatic crisis. 

Turkish authorities say the journalist was killed inside the Saudi consulate by a group of hitmen traveling from Riyadh, which has insisted without evidence that Khashoggi disappeared after leaving the consulate.