Al-Qaeda militants launched a surprise attack against army bases in southern Yemen, killing 78 soldiers, seizing weapons and parading 55 troops they had taken captive through the center of a town under their control, military officials said.
The battle in Abyan province shows how militants have taken advantage of the political turmoil created by the year-long uprising against then-President Ali Abdullah Saleh who last month handed over power to a successor.
The scale of Sunday's attack points to the combat readiness of the militants as they launch more and more attacks in a region that the United States considers a key battleground in the war on al-Qaeda.
Military officials in Yemen said 28 militants also died in the fighting and scores were wounded on both sides. Medical officials confirmed the latest death toll.
The captives were paraded late on Sunday through the streets of Jaar, a nearby town that has been under al-Qaeda's control for nearly a year.
The officials spoke on condition of anonymity because they were not authorized to speak to the media.
Militants seized control of Zinjbar in May and Jaar the previous month as security officials were focused on putting down a rebellion against longtime leader, Saleh.
The officials said the militants attacked the army bases outside Zinjibar from behind, taking the troops by complete surprise.
Saleh stepped down last month in a U.S.-backed power transfer deal that Washington hoped would allow Yemen's new leaders to move against al-Qaeda. But the fighting highlights the difficulties faced by his successor Abed Rabbo Mansour Hadi in combatting the militant movement and restoring state authority in the lawless south.
The military officials said the militants were able to seize armored vehicles, artillery pieces, assault rifles and rockets from the stores of an army base they attacked. Some of the heavy weapons were later used against the troops, causing most of the casualties.
A Defense Ministry statement on Sunday said the fighting began when militants detonated "booby trapped vehicles" at an army base in the region of Koud near Zinjibar. The wording of the statement suggested that the base had been occupied by the militants before army forces regrouped and took it back. The fighting lasted the whole day, only stopping by sunset.
Hadi meanwhile said in televised comments that fighting al-Qaeda and restoring security in the impoverished Arab nation were among his top priorities. He spoke during a meeting with leaders of Yemen's political parties.
Saleh during his more than 30 years in power tolerated radical Islamic groups as part of a delicate balancing act that kept at bay threats to his authority in the fractured nation.
There has been a surge in attacks blamed on al-Qaeda after Hadi's inauguration.