Updated at 2:10 p.m. ET:
Yemen's President Abed Rabbo Mansour Hadi has fled his palace in Aden, after Houthi rebels appeared to be closing in on the southern port city. It's not clear if the embattled president has left the city or the country.
U.S. State Department spokesperson, Jen Psaki, says the administration was in touch with Hadi earlier today. She confirmed that he is no longer at his Aden residence, but cannot confirm any additional details about his location.
Earlier, The Associated Press, which cited Yemeni security and port officials, said Hadi had left the country by boat, however those reports could not be confirmed. The news service says Houthi rebels captured the city's airport, and that Aden, the country's economic hub, could soon fall.
The Shiite rebels captured the capital city, Sanaa, in September and have swiftly advanced toward Aden, where Hadi encamped after being pushed from power.
Rebels also reportedly were battling pro-government security forces guarding the president's palace in Aden, and seized an airbase that was critical to U.S. drone operations against al-Qaida.
On Tuesday, Hadi appealed to the U.N. Security Council to authorize a military intervention to prevent Yemen from "sliding into more chaos and destruction," according to The Guardian.
Reuters reports that Saudi Arabia is moving heavy military equipment, including artillery, to its border with Yemen. Saudi Arabia says the buildup at the border is purely defensive.
Gregory Johnsen, a Yemen expert with Buzzfeed, tells NPR's Michele Kelemen that Saudi Arabia is saber rattling, and that it would be a huge miscalculation if it sends troops into Yemen.
Johnsen, the author of The Last Refuge: Yemen, al-Qaeda, and America's War in Arabia, says the increasing chaos in Yemen could spill over into the region, especially between Sunni Saudi Arabia and Shi'ite Iran, which Johnsen says is providing aid Houthi rebels.
"What we're seeing are regional rivalries, particularly between Saudi Arabia and Iran, are being grafted on to this local domestic conflict." Johnsen says that when you put all the different elements together, it's a "witch's brew."
The ongoing volatile political and security situation has forced the U.S. to pull all its remaining personnel — civilian, military and intelligence — out of the country. The move could have an impact on U.S counter-terrorism efforts against al-Qaida in the Arabian Peninsula, considered one of the most dangerous offshoots of the terror group.
There are growing concerns the deteriorating situation could create a power vacuum in Yemen. Nabeel Khoury, with the Atlantic Council, tells NPR that the chaos and a looming civil war will produce more terrorism by groups such as the self-proclaimed Islamic State, also known as ISIS.
"We've seen now that ISIS has established a small foothold in Yemen, this will likely grow, a lack of political stability means extremism thrives," Khoury says.