Al-Qa'ida's front group in Yemen has been routed from two major strongholds in the south that it had seized during last year's political turmoil.
The militant group says it withdrew from the towns of Jaar and Zinjibar to "spare bloodshed," but it has also vowed to attack Yemen's capital, Sanaa.
Gamal al-Aqil, the governor of Abyan province, says Yemeni troops are in full control of Zinjibar, the provincial capital. The military has also regained control of Jaar, another stronghold of al -Qa'ida to the north of Zinjibar today.
The withdrawal is a major victory in a US-backed offensive to regain control of large swathes of territory from al-Qa'ida in the Arab world's most impoverished country.
The capture of Jaar and Zinjibar came after weeks of heavy bombardment and shelling of al-Qa'ida positions, with the help of dozens of US troops stationed at a command centre in an air base near the conflict zone deep in the southern desert. Troops also liberated a vital highway that links Jaar with the port city of Aden, according to the Yemeni Defence Ministry.
Al-Qa'ida in Yemen, which the US considers the most dangerous offshoot of the terror network, had exploited the country's political turmoil that resulted from last year's uprising against the former leader Ali Abdullah Saleh to seize major population centres in the southern province of Abyan. That raised fears it could use the area as a foothold to launch more attacks on US targets.
The latest strikes leave al-Qa'ida scattered in smaller towns, valleys, desert and mountainous areas - similar to the group's situation before the revolt that ousted Saleh began in February 2011.
The militant group said it had retreated from Zinjibar and Jaar to "spare bloodshed," but it also threatened to retaliate by attacking Yemen's capital, Sanaa. In an emailed statement, the group addressed the Yemeni leadership as "crusaders and American agents" and warned "we will chase you in your cities and palaces."
Yemeni troops and allied tribesmen swooped into Jaar in a surprise dawn attack after hours of heavy shelling by artillery and rockets from hilltop positions, military officials said. Pro-government fighters rode into town from three different fronts in trucks, while dozens of tanks were used to block the town's entry and exit points, they added.
Residents flocked to the town's centre, firing guns in the air in celebration. Others looted warehouses filled with humanitarian supplies delivered by relief groups, Waleed Mohammed, a resident said.
Gamal al-Aqil, the governor of Abyan province, says Yemeni troops had dealt "painful blows" to al-Qa'ida "in their biggest dens in Abyan".
"We called the operation the Golden Swords," he said.
Officials and witnesses said that some 500 al-Qa'ida militants, including foreigners, fled the town after spray painting walls and store shutters with slogans in red saying, "al-Qa'ida has withdrawn. Al-Qa'ida was not defeated".
The victories capped weeks of fighting as Yemen's new president Abed Rabbo Mansour Hadi has pledged to uproot al-Qa'ida from the south with help from the United States as part of a new cooperation following the ousting of Ali Abdullah Saleh amid a popular uprising.