ADEN (AFP) ― Yemen’s army, with the backing of U.S. experts, is slowly gaining ground in its southern offensive against al-Qaida, diplomats and officials said on Wednesday, as the death toll in five days of fighting rose to 144.

The Yemeni air force late afternoon launched two air strikes targeting al-Qaida positions near Loder in Abyan province, killing 16 jihadists and wounding 14 others, according to a spokesman for the Popular Resistance Committees, a local militia.

On the ground, a military official said the army on Wednesday had advanced towards the southeastern entrance of Zinjibar, which was captured by al-Qaida militants a year ago, following clashes that left six soldiers wounded.

“The army is deployed at the entrances of the city. It advances during the day and tactically retreats at night out of fear of terrorist attacks,” an officer on the ground at Zinjibar, capital of southern Abyan province, told AFP.

The military source said a force of around 20,000 soldiers from all regions in the south are engaged in the all-out operation launched on Saturday to retake al-Qaida strongholds in Abyan province.

They are backed by armed local militia consisting of residents of towns and cities determined to put al-Qaida to flight.

Another 13 people were killed in fighting on Wednesday, most of them jihadists, officials and tribal sources said.

According to Western diplomats in Sanaa, U.S. experts have been deployed on ground, mainly at Al-Anad airbase in the nearby Lahij province, to offer advice to Yemeni troops.

At the same time, U.S. drones are launching surgical strikes targeting the militants, according to witnesses, who have also reported that U.S. naval units are bombing jihadists’ positions from the sea.

AFP has not been able to confirm this information from official sources.

On Sunday, John Brennan, U.S. President Barack Obama’s top counter-terrorism aide held talks in Sanaa with Yemeni President Abdrabuh Mansur Hadi on “combatting terrorism” and attempts by Yemen’s army to crush the local branch of al-Qaida, official media said.

The offensive was launched after newly-elected Hadi vowed to fight the network and followed days after the White House announced that a plot by al-Qaida in the Arabian Peninsula (AQAP) to blow up a U.S. airliner had been successfully thwarted.

A senior U.S. official told the New York Times that a bomb for the would-be attack was sewn into “custom fit” underwear that would have been difficult to detect even in a careful pat-down at an airport.

The paper said a double agent managed to spend weeks with AQAP before handing over information that allowed the United States to launch a drone strike in Yemen on May 6 that killed Fahd al-Quso, a senior figure who was wanted for the 2000 bombing of the USS Cole in Yemen.

Quso’s name figured on an FBI list of most wanted terrorists, along with a reward of up to $5 million for information leading to his arrest.

On May 12, U.S. drones launched another two air strikes, killing a total of 11 suspected al-Qaida jihadists in eastern Yemen.

On the ground, the army backed by local militiamen on Wednesday exchanged artillery fire with al-Qaida insurgents in an area surrounding Mount Yasuf, overlooking Loder, northeast of Zinjibar, witnesses said.

A member of the Popular Resistance Committees, a militia formed by local residents, told AFP that al-Qaida militants had at dawn fired artillery shells at troops and militiamen stationed atop Mount Yasuf, killing two armed residents and wounding four.