Suspected Al Qaeda gunmen have overrun the southern Yemeni city of Zinjibar after heavy clashes with security forces left 16 dead, an official told AFP Sunday.
Two other officials said that fighting raged in the city on Friday and Saturday, with 15 soldiers and one civilian killed in the violence.
"About 300 Islamic militants and Al Qaeda men came into Zinjibar and took over everything," one resident told Reuters Sunday.
A security official told AFP that he estimated over 200 militants attacked the city. Another official said the attackers "took over all government facilities".
Residents also said the gunmen freed dozens of prisoners from the city's main prison and that battles were still ongoing Sunday morning.
Opposition to Yemen's President, Ali Abdullah Saleh, accused the leader that he allowed the city to fall to raise fears of Al Qaeda and boost his international support, AFP reports.
The clashes came while Saleh and the country's most powerful tribal leader agreed on Saturday to end five days of gunbattles between forces loyal to each side that killed 124 people and pushed the country's political crisis closer to civil war.
Although it could prevent bloodshed, Saturday's agreement will do little to solve the wider crisis, with Saleh rejecting efforts to negotiate his exit.
The week's battles began when Saleh's security forces attacked the home of Sheik Sadeq al-Ahmar, head of the powerful Hashid tribal confederation and an uneasy ally who abandoned the president and joined his opponents. Tribal fighters came to al-Ahmar's defense and seized a number of government buildings in the Hassaba neighborhood of the capital, Sanaa, during intense clashes.
Fighting then spread outside the capital when tribal fighters seized two army posts north of the city on Friday.
A member the committee of tribal leaders who brokered Saturday's deal said the sides had agreed to withdraw their forces from the neighborhood starting Sunday morning.
The mediation committee will take control of the government buildings seized by tribal fighters so civilians can return to the area, the mediator said.
An aide to al-Ahmar confirmed the agreement's details.
"The committee reached an agreement, and we will abide by it," he said.
Both spoke on condition of anonymity because they were not authorized to talk to the media.
But a Yemeni rights activist said Sunday that a brigade of the powerful Republican Guard run by the son of Saleh has defected to the opposition in a southern province.
It's the first reported defection among the elite troops, which have been the core of Saleh's hold on power despite three months of massive street protests and defections by some military and tribal allies.
Activist Abdul-Rahman Ahmed says a letter from Brig. Gen. Ibrahim al-Jayfi, commander of the Guard's Ninth Brigade was read to thousands of protesters in the provincial capital of Damar on Sunday.
Experts say the uprising's future will be determined by the number of tribes and security forces that turn against Saleh. Many already have, including the Hashid confederation, to which Saleh's tribe belongs. Some army units have also left Saleh to back the protesters, though they did not join the fight against his forces.
The Associated Press contributed to this report.