ADEN, Yemen (AP) -- This port city, perched on an extinct volcano protruding into the Arabian Sea on Yemen's far southern edge, has become perhaps the last refuge of the country's embattled president, and it feels like now all his enemies are bearing down on it.
Driven out of the capital, Sanaa, by Shiite rebels who have taken over much of the north, President Abed Rabbo Mansour Hadi and the remains of his government have made Aden their provisional capital. If they lose here, Hadi -- the man the U.S. had hoped would stabilize the chaotic nation and fight al-Qaida's powerful branch -- likely will fall, plunging Yemen into a civil war.
In his first speech since fleeing Sanaa, Hadi on Saturday denounced the rebel takeover as "a coup against constitutional legitimacy" and declared Aden the country's "temporary capital."
The city is visibly expecting assault, whether from the forces of Hadi's rival, ousted President Ali Abdullah Saleh, who has allied himself with the Shite rebels, or from al-Qaida militants. Army and police forces loyal to Hadi and their allied militiamen patrol Aden's streets and man checkpoints at key locations. Tanks guard roads leading to the city and children are largely staying home from school.
"There are great fears that plans are underway for Aden to meet the same fate as Sanaa," Nayef al-Bakry, Aden's deputy governor, told The Associated Press. Referring to Saleh and the Shiite rebels, "they want to extend their reach on both the ground and on the coast."
Early this week, Hadi's forces fended off an attempt by police commandos loyal to Saleh to capture the airport. But there are still two army units loyal to Saleh in the city. And on Sunday, the Shiite rebels, backed by forces loyal to Saleh, seized Yemen's third largest city, Taiz, 140 kilometers (85 miles) to the northwest of Aden. Officials here fear it is a prelude to an attack on Aden.
The takeover of Taiz, known as the "gateway to the south," followed the arrival there two days ago of a column of 20 armored fighting vehicles and 30 truckloads of Shiite rebel fighters and pro-Saleh troops.
Equally worrying, al-Qaida militants on Friday took a city on Aden's doorstep, al-Houta, capital of neighboring Lahj province. Al-Qaida fighters now have positions only 20 kilometers (12 miles) from Aden. Hadi on Saturday accused Saleh's forces, which had held al-Houta, of intentionally surrendering it to the militants to create even more chaos, and he sent a force led by his defense minister, Maj.-Gen. Mahmoud al-Subaihi, to retake the city.
The drama in the south is just one part of Yemen's turmoil.
Around the country, al-Qaida militants have been battling the Shiite rebels, known as Houthis, and in some places Sunni tribesman have allied with the militants. A new alarming sign came Friday when suicide bombers hit two mosques in Sanaa controlled by the Houthis, killing more than 130 people in a devastating attack that may signal the emergence of a new branch of the Islamic State group, the extremists who are seeking to supplant al-Qaida region-wide as the flagship for Islamic militants.
Hadi fled Sanaa last month after escaping house arrest under the Houthis, who took over the capital in September. Aden is Yemen's second most important city and the country's economic hub, and as long as Hadi was here he could reasonably claim to still be president. Moreover, he chose Aden because as a southerner he has considerable support in the region.
Aden has been at the center of trade in the Indian Ocean for centuries. Its populace has long seen itself as more sophisticated and distinct from mountainous, tribal, inward-facing Sanaa.
Aden was the capital of an independent South Yemen for decades until unification in 1990. Today, secessionist sentiment remains strong -- many pro-Hadi militiamen in the streets wave the red, white, black and blue flags of the former South Yemen.
Billboards welcoming Hadi to the city hang on many streets, along with pro-Hadi graffiti on the walls. Since he arrived, Hadi has issued calls for volunteers to join the army, a move his camp depicts as an attempt to build a military that stands above tribal, personal or regional loyalties. So far an estimated 20,000 men in Aden alone have volunteered.
"The protection of Aden is a task the president must prioritize," Hadi adviser Sultan al-Atwany told the AP. "We need to build a new army, one that owes allegiance to the country and not anyone else."
But the bulk of Aden's security is in the hands of pro-Hadi militiamen grouped in what are officially known as the "Popular Committees," a rag-tag army of southern tribesmen who took part in the military campaign against al-Qaida in nearby Abyan and Shabwa provinces in 2012.
Hadi came to office in the aftermath of the 2011 Arab Spring uprising against Saleh, the autocrat in power since 1978. An accord brokered in 2012 by U.S.-allied Gulf nations removed Saleh and installed Hadi, but Saleh remained in the country and his loyalists continued to hold powerful positions in the government, the military and the security forces. Saudi Arabia and the U.S. strongly backed Hadi, and the new president proved a stauncher ally to the U.S. than Saleh in the fight against al-Qaida's branch in the country.
Ever since, Hadi has accused his ousted predecessor of undermining him. Saleh is widely thought to be seeking to avenge his ouster and to ensure that his son, career army officer Ahmed, is Yemen's next president. Now Saleh has openly allied himself with the Houthis, using his influence in the military to facilitate their expansion. Like the Houthis, Saleh follows the Shiite Zaydi sect which exists almost exclusively in Yemen.
Hadi's forces were able to fend off the airport assault by the pro-Saleh police commandos on Thursday and even subsequently took the commandos' base. But the extended public gunbattle underlined the fragility of the city's defenses.
During the fighting, a warplane flown by Saleh's loyalists attacked Hadi's residence. The three bombs missed the palace, and Hadi was not there at the time. But the raid signaled that his opponents are aiming to kill him -- or at least show him they can.
Meanwhile, Aden also faces a looming threat from al-Qaida.
The group's capture of nearby al-Houta is its first major seizure of territory since 2011, when it held parts of nearby Abyan and Shabwa provinces for more than a year until Hadi's forces drove them out with U.S. backing.
Aden has since 2011 seen an uptick of suicide bombings, assassinations and attacks targeting intelligence and military officials -- mostly blamed on al-Qaida. The security and military officials said Aden has in recent months seen a steady infiltration of al-Qaida fighters.
On Thursday, at least 300 inmates in Aden's main jail -- including several al-Qaida fighters and leaders -- were freed by forces loyal to Saleh, said officials, who spoke on condition of anonymity because they were not authorized to speak to journalists.
The officials said al-Qaida in Yemen was weakened since its expulsion from Abyan and Shabwa but has been regrouping, in part energized by opposition to the Shiite Houthis.
Sunni tribesman in Yemen's north have struck alliances, albeit temporary, with al-Qaida to keep the Houthis from advancing. Al-Qaida has also been rebuilding in the strategic and vast southern province of Hadramout, which borders Saudi Arabia.
"There are signs of security vacuums and there are al-Qaida bands operating in some areas," Hadramout Governor Adel Bahameed told the AP in Aden. "We are doing everything we can to contain them."