The fighting erupted when militants from Ansar al-Sharia (Partisans of Sharia) launched a dawn attack on the camp in Abyan province, about 120 km (75 miles) from the southern port city of Aden.
The group seized control of a significant amount of territory in Abyan during the turmoil that led to the replacement of President Ali Abdullah Saleh by his deputy, a deal that Saudi Arabia and Washington hope will prevent al Qaeda from getting a foothold near key oil shipping routes.
The conflict with Islamists in the south is only one of several challenges facing the new president, Abd-Rabbu Mansour Hadi, who took office vowing to fight al Qaeda, only to have more than 100 soldiers killed in a series of attacks in his first days in power.
Eighteen fighters were killed in Monday's clash with the army and five when warplanes bombed a checkpoint they were holding, officials and residents said. Nine soldiers and six tribesmen fighting alongside them were also killed.
A military official said the army drove the fighters away from the area around the camp. The militants said in an emailed statement that none of their fighters was killed in the clash, and threatened to attack Lawdar.
Intermittent gunfire was heard throughout the afternoon hours while the military carried out a second air strike, but no casualties were reported, officials and residents said.
Mohammed Nasser, a resident of Lawdar, speaking by telephone with the sound of artillery and small arms fire audible, said the fighting lasted three hours.
A local official said tribal militiamen joined the fighting alongside the military, and that at least 10 soldiers and tribesmen were wounded.
Washington, which has pursued a campaign of assassination by drone and missile against alleged al Qaeda targets in Yemen, wants Hadi to reunify a military that split between Saleh's foes and allies last year, and focus it on "counter-terrorism".
Yemen's main airport in the capital, Sanaa, was paralyzed for a day after Hadi sacked the air force commander, a relative of Saleh, on Friday, and pro-Saleh officers responded by blockading the airport with vehicles.
A government official said they backed down only after warnings from the United States and the Gulf countries which crafted the deal that made Hadi president.
In the capital Sanaa, a military committee tasked with restructuring the armed forces oversaw the evacuation of troops and dismantling of some checkpoints belonging to rival divisions of the military, an official said.
The official, who asked not be named, said checkpoints controlled by the Republican Guard, led by Saleh's son, and renegade general Ali Mohsen al-Ahmar were being dismantled.
Separately, unidentified gunmen attacked a military checkpoint in Aden, killing two soldiers, a security official said. He gave no further details.
The country's top oil committee, chaired by Prime Minister Mohammed Basindwa, met on Monday to decide crude oil exports in June, Saba state news agency reported.
China's Unipec, the trading arm of top Asian refiner Sinopec Corp, won a bid to buy 100,000 barrels a day of Masila crude in June, the agency said.
(Reporting by Mohammed Mukhashaf; Writing by Joseph Logan and Mahmoud Habboush; Editing by Alison Williams)
Reuters
