An employee walks past crude oil storage tanks at the Juaymah Tank Farm in Saudi Aramco's Ras Tanura oil refinery and oil terminal in Ras Tanura, Saudi Arabia, on Oct. 1, 2018.

Saudi Arabia kick-started Aramco's initial public offering (IPO) on Sunday as its market regulator approved the oil giant's application to list on the domestic bourse and create the world's most valuable listed firm.

A statement from the Capital Market Authority (CMA) did not give a time frame or say how much Aramco would sell, but sources have told Reuters the oil company could offer 1% to 2% of its shares on the local bourse, raising as much $20 billion to $40 billion.

Confirmation of the share sale in Saudi Arabian Oil Co., or Aramco, as the oil giant is usually known, comes about seven weeks after crippling attacks on its oil facilities, underlining Saudi Arabia's determination to push on with the listing regardless.

The IPO of the world's most profitable company is designed to turbo charge Crown Prince Mohammed bin Salman's economic reform agenda by raising billions to diversify the kingdom, whose dependency on oil was highlighted by the production impact of the Sept. 14 attacks.

The CMA said its board "has issued its resolution approving the Saudi Arabian Oil Company (Saudi Aramco) ... application for the registration and offering of part of its shares."

The authority said approval would remain valid for six months.

Saudi Aramco will release the IPO prospectus on Nov. 10, Saudi-owned news channel Al-Arabiya said on Sunday, citing sources.

The listing announcement had been expected on Oct. 20 but was delayed after advisers said they needed more time to lock in cornerstone investors, three sources told Reuters.

To help get the deal done, Saudi Arabia is relying on easy credit for retail investors and hefty contributions from rich locals.

Prince Mohammed gave the green light on Friday for the IPO to go ahead, Reuters reported, citing sources.

Although he put a $2 trillion valuation on the company in early 2016, bankers and company insiders say Aramco's value is closer to $1.5 trillion.

A growing movement to fight climate change and embrace new "green" technologies have put some fund managers, particularly in Europe and the United States, off the oil and gas sector.