More than half of Saudi oil production was hit by the drone attacks.

Saudi Arabia said on Tuesday its oil output would be back to normal by the end of the month, with half the production lost in weekend attacks on two key facilities already restored.

Energy Minister Prince Abdulaziz bin Salman, who was only appointed to the role earlier this month, said that the world's top energy exporter had dipped into its strategic reserves to maintain supply to clients.

"I have good news for you... the oil output to international markets is back to what it was before the attack," he said.

"During the past two days the damage was contained and 50 percent of the production has been recovered," he added.

"Production will be back to normal by the end of September."

But as the US points the finger of blame at Saudi Arabia's regional rival Iran, the minister -- the son of King Salman -- refused to be drawn on who was responsible for the Saturday's strikes which roiled global energy markets.

"We don't know who is behind the attack," he said, adding that the kingdom wants "proof based on professionalism and internationally recognised standards".

Saudi authorities were also bullish on plans for the mega stock listing of oil giant Aramco, which was thought to be imperilled by the attack.

"The IPO will continue as is, we won't stop anything," said Aramco chairman Yasir al-Rumayyan.

Riyadh pumps some 9.9 million barrels per day (bpd) of which around 7.0 million bpd are exported, mostly to Asian markets.

The strikes took out half its output, some six percent of global oil production.