Crude oil prices rose sharply after Saturday's attacks on two oil facilities in Saudi Arabia. 

The Brent index surpassed $71 a barrel shortly after Monday's trading session began in London on Monday, up 18% from last week. 

In New York, the WTI futures price index jumped 15% to over $63 a barrel. 

Prices eased as the trading session continued. But at 11am, the future price of oil in key markets was still about 10 percent higher than the week before. 

The Saudi government has revealed that the attacks have caused its daily output to fall to about half. 

Market analysts say an announcement by the United States that they will prepare to release their oil reserves has helped to curb rising prices. New highs are possible until more details about Saudi Arabia's production capacity are known.

Trump 

US President Donald Trump said his government was ready to respond to attacks on oil facilities in Saudi Arabia.

He posted on Twitter that there are reasons to believe that you know who is to blame and what measures are ready to be taken pending confirmation. 

Trump also said the United States is waiting for Saudi Arabia to express its views on who they believe is the perpetrator of the attack and how they should proceed. 

Presidential Councilor Kellyanne Conway told Fox News television on Sunday that Secretary of State Mike Pompeo had "made it clear that the Iranian regime is responsible" for the attacks. 

On the possibility of an offensive against Iran, Conway said that "the president, his national security team and secretary Pompeo have many options on the table." 

Houthi insurgents, backed by Iran in Yemen, took responsibility for the attacks. Iran denies involvement.