Trump instructs Mnuchin to 'substantially increase' sanctions on Iran

US President Donald Trump on Wednesday instructed Steven Mnuchin, the US Secretary of the Treasury to "substantially increase" sanctions on Iran.

"I have just instructed the Secretary of the Treasury to substantially increase Sanctions on the country of Iran,'' Trump tweeted.

This comes after the US Secretary of State Michael Pompeo embarked on a three-day visit to Saudi Arabia and UAE on Wednesday amid rising tensions in the Gulf region over a recent drone attack on two Saudi Aramco oil facilities.

Earlier on Sunday, Pompeo had accused Iran of the drone attacks on the Saudi oil facilities."Tehran is behind nearly 100 attacks on Saudi Arabia while Rouhani and Zarif pretend to engage in diplomacy. Amid all the calls for de-escalation, Iran has now launched an unprecedented attack on the world's energy supply. There is no evidence the attacks came from Yemen," Pompeo tweeted.

Iran has since dismissed all allegations against it and rejected Pompeo's statements which hold Tehran responsible for the attacks.

Saturday morning's drone attacks had knocked off half of the Kingdom's oil production. Yemen's Houthi rebels had claimed responsibility for it.

The Iran-US relationship has shown strain in recent times, especially after Washington's exit from the landmark Iran nuclear deal last year.