WASHINGTON (BLOOMBERG) - Saudi Arabia will show evidence of Iran's involvement in the devastating attack against major oil facilities that caused global crude prices to soar, state television reported.

A Saudi defence ministry spokesman said it will hold a news conference on Wednesday (Sept 18) evening outlining Iran's role as well as the weapons used in the attacks, the report said, without giving a specific time.

The US - a close ally of Saudi Arabia - has blamed Iran for the highly coordinated and successful attacks, which were initially claimed by Houthi rebels in Yemen that have been fighting Saudi forces there since 2015.

Iran launched an "unprecedented attack on the world's energy supply," US Secretary of State Mike Pompeo said on Twitter, without giving evidence to back up the allegation.

Iran's foreign minister, Mohammad Javad Zarif, has denied any role. He said on Twitter that the US campaign of "maximum pressure" against Iran has turned into one of "max deceit", and urged Washington to once again engage in talks.

The Sept 14 attack on two of Saudi Arabia's largest crude oil production plants was the single biggest sudden disruption on record, surpassing shocks during the Gulf War in 1990 and the loss of Iranian output from the 1979 Islamic Revolution.