Attacks such as the one on Saudi oil facilities which last month sent oil prices up by as much 20% may continue if there is no concerted international response, Saudi Aramco's Chief Executive Amin Nasser said on Wednesday.

"An absence of international resolve to take concrete action may embolden the attackers and indeed put the world's energy security at greater risk," he told the Oil & Money conference in London in rare political comments.

He added Aramco was on track to regain its maximum oil production capacity of 12 million barrels per day by the end of November.