Yemeni government troops battled Al Qaeda militants in heavy fighting Wednesday that left 31 people dead, raising the death toll from three days of clashes to at least 158, military officials said.

The fighting, which broke out Monday with an ambush on an army post, is centered in and around the town of Lawder in the country's nearly lawless south. Of those killed on Wednesday, 28 were Al Qaeda militants and three were civilians fighting alongside the army, the officials said. Six civilians were also wounded.

The officials spoke on condition of anonymity because they were not authorized to speak to the media.

The Defense Ministry said in a statement that the 28 militants killed Wednesday included two senior members of the terror network in the area. It identified them as Imad al-Manshaby and Ahmed Mohammed Taher.

In cities like Lawder, which is in Abyan province, residents have become fed up with the government's inability to protect them and, in a country where most adult males possess weapons, have taken up arms to protect themselves.

There are an estimated 300 mostly young men armed with assault rifles and rocket-propelled grenades who have joined the government side in the fight. But they are running low on ammunition and food supplies, according to one of their leaders, Jihad Hafeez. Many of the town's residents have left the city to escape the fighting, he said.

The fighting is the latest in a series of bloody confrontations between government forces and Al Qaeda-linked militants, who have taken advantage of the turmoil caused by the popular uprising against longtime ruler Ali Abdullah Saleh to seize control of towns and swaths of territory in the south. Army troops are using rockets and artillery in the three-day battle.

Al Qaeda's branch in Yemen, known as Al Qaeda in the Arabian Peninsula, is one of the movement's most dangerous offshoots.

Saleh, who left office in February as part of a U.S.-backed deal, was Washington's longtime partner in the fight against the terror network's branch in this impoverished Arab nation. But Saleh was frequently found to be unreliable, turning a blind eye to the growing strength of militant groups as part of an elaborate balancing act to maintain his grip on the fractured nation located in the southern part of the Arabian Peninsula.

Al Qaeda was once present in Lawder, but in July residents drove them out. The militants have since been trying to regain their foothold in the town, which has a population of about 30,000.

Lawder is strategically located along a major highway that links Abyan's provincial capital of Zinjibar, an Al Qaeda stronghold, to the provinces of Hadramawt, Bayda and Shabwa, where the group also is active. The area is now a patchwork of government- and militant-controlled towns.

Yemen's popular uprising, which was inspired by Arab revolts elsewhere, succeeded in pushing Saleh from power. His successor and former deputy, Abed Rabbo Mansour Hadi, was later rubber-stamped as president in a single-candidate nationwide vote that was part of the power transfer deal.

Washington hopes that Hadi can bolster the government's authority and make good on his pledges to fight Al Qaeda.

But in addition to his war with the militants, he also faces a challenge from Saleh loyalists and a crippled economy.