US is ready to help protect Saudi security: Trump tells Crown Prince

US President Donald Trump told Saudi Arabia's crown prince that Washington was ready to cooperate with the kingdom to protect its security, following drone attacks on Saudi oil plants on Saturday, state news agency SPA reported.

Trump also told Crown Prince Mohammed bin Salman in a call that assaults on Saudi oil facilities had a negative impact on the US and global economies, SPA said in an Arabic-language statement.

The White House said on Saturday that the United States was committed to keeping oil markets well-supplied in the wake of an attack on Saudi Arabian oil plants by Yemen's Iran-aligned Houthi group.

"The United States strongly condemns today's attack on critical energy infrastructure," White House spokesman Judd Deere said in a statement. "Violent actions against civilian areas and infrastructure vital to the global economy only deepen conflict and mistrust."

Deere confirmed that US President Donald Trump had spoken earlier on Saturday with Saudi Crown Prince Mohammed bin Salman.

Saudi Arabia's oil production and exports have been disrupted, said three sources familiar with the matter, after drone attacks on two Aramco plants on Saturday, including the world's biggest oil processing facility.

One of the sources said the attacks have impacted 5 million barrels per day of oil production -- almost half the kingdom's current output. The source did not elaborate.

Saudi Aramco operates the world's largest oil processing facility and crude oil stabilisation plant in the world at Abqaiq, in eastern Saudi Arabia. The plant has a crude oil processing capacity of more than 7 million barrels per day.