Powerful Crown Prince Mohammed bin Salman pledged a "moderate, open" Saudi Arabia on Tuesday, breaking with ultra-conservative clerics in favour of an image catering to foreign investors and Saudi youth.

"We are returning to what we were before -- a country of moderate Islam that is open to all religions and to the world," he said at an economic forum in Riyadh.

"We will not spend the next 30 years of our lives dealing with destructive ideas. We will destroy them today," he added.

"We will end extremism very soon."

The crown prince's statement is the most direct attack by a Saudi official on the Gulf country's influential conservative religious circles, who have for decades wielded influence on policy.

While the Saudi government continues to draw criticism from international rights groups, Prince Mohammed has pushed ahead with reforms since his sudden appointment on June 21.

Authorities have vied to modernise certain sectors in the kingdom, hinting that long-banned cinemas would soon be permitted as part of ambitious reforms for a post-oil era that could shake up the austere kingdom's cultural scene.

The young prince is widely regarded as being the force behind King Salman's decision last month to lift a decades-long ban prohibiting women from driving.

Earlier Tuesday, Saudi Arabia's Public Investment Fund announced the launch of an independent economic zone along the kingdom's northwestern coastline.

The project, dubbed NEOM, will operate under regulations separate from those that govern the rest of Saudi Arabia.

Monitors, including Amnesty International, say Saudi Arabia has in parallel stepped up its repression of peaceful rights activists.

Saudi authorities last month arrested dozens of activists, including clerics, without disclosing any charges against them.