* Yemen pushes back Islamist militants in fighting
* Air strikes help fighters capture hilltop (Adds interior ministry statement)
By Mohammed Mukhashaf
ADEN, Yemen, May 16 (Reuters) - Yemeni troops, backed by local tribesmen, captured a strategic mountain that controls access to cities long held by al Qaeda-linked militants amid heavy fighting that has killed at least 24 people, residents and local officials said.
The fighting is part of an army offensive against Ansar al-Sharia, a militant group that has seized swathes of territory in Yemen's south during a year of political upheaval that toppled President Ali Abdullah Saleh.
Saeed al-Dhailie, a spokesman for a committee set up to mobilise residents against Ansar al-Sharia in Lawdar, said local fighters had managed to capture the Yasouf mountain, a strategic vantage point above the city, after heavy fighting.
"This morning the army, assisted by armed tribesmen from Lawdar, succeeded in driving al Qaeda militants off Yasouf mountain," Dhailie told Reuters.
"Aerial and artillery attacks by the army started after the dawn prayer. Then we moved up the mountain, official forces and tribesmen side by side. By 11 a.m. we had driven al Qaeda away and recaptured the mountain," he said.
Dhailie said the militants were using Soviet-era heavy machineguns known as Duskas and heavy artillery looted from army camps they had raided in recent months.
"It's bloody. Al Qaeda are fighting to the death," he said.
Local officials and residents said 16 militants were killed in fresh clashes outside Lawdar, including a local commander of Ansar al-Sharia known as Samir Salem al-Moqayda. Ansar al-Sharia has been trying to capture Lawdar for weeks, without success.
They said eight Yemeni troops and members of the popular committees have also died in the fighting and five more were wounded.
The United States and Saudi Arabia, the world's top oil exporters, have been alarmed by the growing strength of the militants near shipping lanes in the Gulf of Aden and the Red Sea.
Yemen's interior ministry said security services in Taiz had received information that 20 members of Ansar al-Sharia were present in the province, which until now has seen no militant activity.
"The security apparatus in the province of Taiz has discovered the presence of 20 militants from Ansar al-Sharia in the Mawiyah district. Security is working to pursue these elements and arrest them," the ministry said on its website.
The United States has stepped up air strikes against suspected members of al Qaeda's Yemen-based wing since President Abd-Rabbu Mansour Hadi was elected in February after months of protests that pushed the country to the brink of civil war.
Military sources said troops were also closing in on the militant stronghold of Jaar and the Abyan provincial capital of Zinjibar. Residents of Jaar said dozens of families were fleeing the town in anticipation of further violence as the army drew nearer.
The Yemeni delegation of the Red Cross urged all sides to protect non-combatants, expressing concern at reports civilian areas had been targeted. Six civilians were killed in a Yemeni air force strike on Tuesday. (Additional reporting by Tom Finn and Mohammed Ghobari; Writing by Sami Aboudi and Isabel Coles; Editing by Michael Roddy)