DUBAI/RIYADH (Reuters) -Nadhmi al-Nasr, the long-time chief executive of the $500 billion NEOM mega-project at the heart of Saudi Arabia's drive to diversify away from oil, has departed, NEOM said on Tuesday without giving a reason.

Pitched as a mix of ‘Blade Runner’ and ‘Jurassic Park,’ Neom is the world’s biggest construction project. Twenty-one thousand people have died so far to make it happen.

Saudi Arabia's ambitious futuristic city plans have been bogged down by delays and changes. The most recent is the departure of its CEO, Nadhmi al-Nasr.

Longtime CEO Nadhmi al-Nasr left Neom, Saudi Arabia’s marquee development, which has been plagued by delays, cost overruns and staff turnover.

Saudi Arabia replaced the executive that was overseeing its plan to build the $1.5 trillion futuristic development known as Neom, in the latest sign that the project is struggling to deliver on its ambitions.

The departure of the longtime CEO marks a major shakeup at Neom, which is a showpiece of Riyadh’s economic ambitions.