Tensions are escalating between two of the biggest powers in the Middle East, Saudi Arabia and Iran. Saudi Arabia ordered all citizens to leave Lebanon after the country's prime minister mysteriously announced he's stepping down. He made the announcement while in Saudi Arabia.

Lebanon is currently on the front lines of a regional conflict between Saudi Arabia and Iran. Secretary of State Rex Tillerson said the United States has been assured that Prime Minister Saad Hariri is not being held against his will.

There have been reports that Saudi Arabian authorities forced Hariri to quit his job and he's being held under house arrest, reports CBS News correspondent Holly Williams. Those reports have not been officially confirmed and the Saudis insist that Hariri is a free man.

We simply do not know exactly what's happened, but the reason this matters is that Saudi Arabia and Iran are fighting a proxy war in the Middle East, vying for power in countries including Syria and Yemen.

Iran has enormous influence in Lebanon via Hezbollah, a group the U.S. considers a terrorist organization. Saudi Arabia could now be challenging that influence and fears it could spark a conflict in Lebanon.

Some believe that Saudi Arabia has been emboldened by recent support from President Trump, who recently tweeted "great confidence" in the Saudi leadership.

I have great confidence in King Salman and the Crown Prince of Saudi Arabia, they know exactly what they are doing.... — Donald J. Trump (@realDonaldTrump) November 6, 2017

All this comes against the backdrop of the rise to power of Saudi Arabia's Crown Prince Mohammad bin Salman who – at just 32 years old – is consolidating power in his hands, including with an anti-corruption campaign that's seen over 200 detained, reportedly including several members of the royal family.