At least two Yemeni soldier have been killed after anti-government fighters attacked a military checkpoint in the country's south, a security official said.
The official, speaking on condition of anonymity, said one of the attackers was also killed in Wednesday's assault in the town of Jaar in the southern Abyan province.
He said the clashes were continuing between fighters believed to have links with al-Qaeda and security forces and that he expected casualties.
Al-Qaeda has stepped up attacks in the impoverished and largely lawless country.
The latest assault came a day after a major military and intelligence operation was launched by Yemeni authorities to track down an alleged Saudi bomb-maker who is a key suspect in a foiled air cargo bomb plot over the weekend.
The hunt for 28-year-old Ibrahim al-Asiri was launched in the provinces of Maarib and Shabwa, a security official told the Reuters news agency.
"Asiri is believed to be hiding and moving with senior al-Qaeda elements such as Nasser al-Wahayshi [the Yemen al-Qaeda leader]. Security intelligence are still tracking them down to exactly identify their whereabouts," the official said.
Yemen is under immense pressure to find those responsible for planting two explosive devices found in air cargo destined for the US late last week.