Saudi Arabia and its allies have launched air strikes in neighbouring Yemen to restore the government that collapsed after Houthi rebels took control of large parts of the country.
Reuters cited al-Arabia TV to report that 150,000 Saudi troops and 100 warplanes are involved in the campaign to which Egypt, Jordan, Sudan and Pakistan are also contributing.
The rebels advanced on the southern city of Aden on Tuesday (25 March) following which Yemen President Abdrabbuh Mansour Hadi fled the country by boat, even as the northern tribesmen placed a bounty of $100,000 (£67,000) on his head.
This is the second time in less than a month that Hadi has been forced to flee a Yemeni city. Last month he managed to escape house arrest in Sana'a and relocated to Aden, after the rebels took control of the capital.
Meanwhile, a US-backed military offensive began at Sana'a airport, when unidentified warplanes attacked it and the al Dulaimi military airbase, Reuters reported.
Saudi Arabia and its allies decided to launch the attack to counter Iran-backed Shi'ite forces from taking Aden, where the president had taken refuge after leaving Sana'a.
Prior to launching the attack, Saudi Arabia's ambassador to the US Adel al-Jubeir said at a press conference in Washington: "The Saudis were part of a coalition of approximately 10 nations determined to blunt the advance of Shi'ite Houthi rebels, who have overrun Yemen's capital and forced the American-backed government into a full retreat," the New York Times reported.
Following this, the White House said in a statement that the US supported the operation and that it had authorised US "logistical and intelligence support".
"While US forces are not taking direct military action in Yemen in support of this effort, we are establishing a Joint Planning Cell with Saudi Arabia to coordinate US military and intelligence support," National Security Council spokesperson Bernadette Meehan said.
Saudi Arabia shares a long border with Yemen and fearing an onslaught by the Iran-backed Shi'ite rebels, the Saudis amassed forces on the Yemen frontier on Tuesday (25 March).
The ongoing civil war in Yemen has made the country a crucial front for the US, but the risk of the current situation spiralling into a proxy war continues, with Iran backing the Houthis, and Saudi Arabia and other regional Sunni Muslim monarchies supporting Hadi.