At least 22 al Qaeda-linked militants and 12 Yemeni soldiers were killed in clashes and air strikes overnight during a U.S.-backed offensive against insurgents in the south of the country, officials said on Saturday.
Fighting erupted late on Friday and carried on into Saturday on the outskirts of the southern city of Jaar, held by Islamist militants who have stepped up their campaign during months of political turmoil.
Government troops, backed by U.S. drone strikes, have been trying to push the insurgents out of strongholds in the country's south, which lies near oil shipping routes through the Red Sea.
Washington and Yemen's neighbor Saudi Arabia both fear the instability in Yemen could give al Qaeda's regional wing a stronger foothold in the region.
"There is heavy fighting, and the armed elements are doing everything possible to stop the advance of (government) troops," a government official told Reuters, on condition of anonymity.
Government forces were about 1km (0.6 mile) from Jaar, he added.
Twelve Yemeni soldiers and 17 militants were killed in the fighting and an air strike killed three militants on the outskirts of the city, the official said.
Another air strike destroyed a vehicle used by militants, killing two people inside in the southern province of Bayda, provincial governor Mohammed al-Ameri was quoted as saying on a defense ministry website.
Insurgents have seized swathes of territory in the south of the impoverished Arab country since mass protests erupted last year against then-President Ali Abdullah Saleh.
Washington has stepped up drone attacks in Yemen since President Abd-Rabbu Mansour Hadi took office in February. The Pentagon said earlier this month it had resumed sending military trainers to the Arab state.
On Saturday, the head of the U.S. Special Operations Forces met Yemen's chief of staff and said the United States was committed to supporting Yemen, the state news agency Saba reported.
General Ken Tovo said the United States "was prepared to provide all necessary assistance to Yemen in fighting terrorism and ensuring the elimination of al Qaeda", the agency said.
Tovo's visit to Yemen followed a trip to the country by FBI director Robert Mueller in April.
On Friday, an army official and residents said troops backed by local tribesmen had killed 10 suspected Islamist militants outside Jaar.
Islamist militants linked to al Qaeda retreated on Thursday from the town of Lawdar, about 80 km north of Jaar, as warplanes attacked and ground troops advanced on insurgent-held towns.