LONDON —Saudi Aramco's chief executive said on Wednesday there would be no impact on the stock market listing plans of the oil giant after attacks on its installations last month, which he blamed on Iran.

Attacks such as those on Sept. 14, which sent oil prices up as much as 20%, may continue if there is no concerted international response, Amin Nasser told the Oil & Money conference in London.

The attacks targeted the Abqaiq and Khurais plants at the heart of Saudi Arabia's oil industry, causing fires and damage and shutting down 5.7 million barrels per day (bpd) of production — more than 5% of global oil supply.

"An absence of international resolve to take concrete action may embolden the attackers and indeed put the world's energy security at greater risk," Nasser said in rare political comments.

"You heard the minister of foreign affairs and I think he spoke enough about (where) the attacks (are) coming from. It’s instigated by Iran for sure, there's no doubt."

Yemen's Houthi group claimed responsibility for the attacks, but a US official said they originated from southwestern Iran. Riyadh blamed Tehran. Iran, which supports the Houthis in Yemen's war, has denied any involvement.

Saudi Arabia has maintained supplies to customers at levels seen before the attacks by drawing from its huge oil inventories and offering crude grades from other fields.

Nasser added that the attacks had no effect on Aramco's revenues because the company continued to supply customers as planned. The attacks also had "no impact on the (initial public offering) whatsoever", he said.

Saudi Arabia is pressing ahead with plans to sell between 1% and 2% of Aramco through a local listing, which might be followed by additional share sales internationally.

An IPO prospectus in Arabic could be released to investors on Oct. 25 and an English one for the wider market on Oct. 27, sources have told Reuters.

Nasser said Aramco was on track to regain its maximum oil production capacity of 12 million bpd by the end of November and that October crude output stood at 9.9 million bpd.

The Kingdom's crude oil production capacity is now 11.3 million bpd, the Energy Minister Prince Abdulaziz Bin Salman said last week. — Reuters