The future of Saudi Arabia's mega-city project NEOM seems uncertain as many of the 19 architecture and design leaders listed on the project's advisory board earlier this month have abruptly withdrawn from participation citing concerns over disappearance and killing of dissident Saudi journalist Jamal Khashoggi.

Apple's chief designer, Jonathan Ive was among the first to withdraw his name from the board. A week after news broke on Khashoggi's disappearance on Oct. 2, Apple confirmed that Ive's inclusion was "a mistake."

Several other prominent design figures, including architect Norman Foster, Carlo Ratti of MIT's Senseable Cities Lab, Ideo president and CEO Tim Brown, and former Uber CEO Travis Kalanick, have distanced themselves from the project as well, according to the Fast Company.

The project lost its only foreign partner when British billionaire Richard Branson suspended his directorships over the Khashoggi case. Earlier this month NEOM's advisory board also lost members including Y Combinator's Sam Altman and former U.S. energy secretary Ernest Moniz.

Saudi authorities have estimated NEOM will cost $500 billion, while estimates have not been released for Qiddiya or the Red Sea Project.

The NEOM project involves the creation of a huge transnational city and economic zone and covers 26,500 square kilometers in Saudi Arabia, Jordan and Egypt.

Khashoggi went missing Oct. 2 after entering the Saudi Arabia consulate in Istanbul.

After weeks of denying any knowledge of the crime, Saudi officials last week said the journalist was killed during a "brawl" in the building.

Turkish police have been investigating the case and Erdoğan said he wants 18 suspects extradited to Turkey from Saudi Arabia to stand trial.