At least 17 militants were killed during Friday's clashes, an official said, adding that fighters who occupied the southern town of Shaqra fled to a mountainous region to the west of it.
The fleeing militants included Jalal al-Baleidi, also known as Abu Hamza al-Zinjibari, the leader of Ansar al Sharia (Partisans of Islamic Law) in Abyan, seeking refuge in tribal areas. The group is an offshoot of al Qaeda.
The U.S.-backed offensive, launched more than a month ago, has so far pushed fighters of Ansar al-Sharia, an offshoot of al Qaeda, from two major strongholds Jaazr and Zinjibr.
But the militants warned they would strike back with attacks on civilian and government targets.
On Thursday, Yemeni soldiers killed at least 40 Islamist militants and captured one of their outposts in heavy fighting in Shaqra.
Thousands of soldiers backed by tanks and fighter jets launched the offensive last month and were joined by local tribesmen opposed to the militants.
The United States has provided training and other support, including drone strikes, concerned that its Islamist foes have gained a new foothold in the Middle East.
U.S. officials say that the new Yemeni President Abd-Rabbu Mansour Hadi is more much more cooperative in the fight against Islamist militancy than his predecessor Ali Abdullah Saleh, who handed power to Hadi this year after months of protests.