Yemeni troops killed four Islamist fighters in a southern town they seized from government control, a local official said on Saturday, but a spokesman for the Islamists denied his side had suffered any casualties.
Yemen's state news agency also reported that outgoing President Ali Abdullah Saleh was heading to the United States, a week after leaving the country for Oman under a plan to end the nation's crisis.
The fighting in Zinjibar, capital of the southern Abyan province where Islamist bands have taken control of swathes of territory in the last seven months, underlines erosion of central authority which fans U.S. and Saudi fears the state may collapse and give al Qaeda a foothold near oil shipping routes.
Those fears are behind their support for the plan to ease Saleh from office after a year of protests demanding he go, punctuated by open warfare between his forces and those of a rebel general and tribal warlords.
Residents in the capital said three large blasts shook the headquarters of that rebel army unit, whose troops then traded fire with plainclothed gunmen on Saturday night.
In Zinjibar, Yemeni troops killed four fighters from Ansar al-Shariah in a skirmish on the eastern edge of the town, which Islamists fighters overran last May, a local official said. One soldier was killed in the fighting late on Friday, he said.
A spokesman for the Islamist group said his side had suffered no casualties, but confirmed the account of a soldier's death.
In London, a foreign office official said on Saturday that Saleh's plane had stopped at a British airport en route to the United States. Yemen's state news agency said he had left the Omani capital Muscat, his home for the past week, to receive medical treatment.
Saleh has transferred some powers to his deputy and enjoys immunity from prosecution under the deal. It established a transitional government including the opposition and envisions restructuring Yemen's armed forces, key units of which are led by Saleh's relatives.
His foes accuse him of deliberately ceding territory to Islamists to make himself indispensable to his former U.S. patrons, and of ultimately aiming to sabotage the political transition and retain power for his inner circle.
A police colonel in Hadramout province was gravely wounded when unidentified attackers shot him with automatic weapons before fleeing on motorcycles late on Friday, a local official said. He blamed the attack on al Qaeda.
Islamist fighters - including a relative of a U.S. citizen whom Washington accused of a leadership role in al Qaeda and assassinated last year - briefly took control of the town of Radda, about 170 km (105 miles) south of Sanaa earlier this month.
(Additional reporting by Mohammed Ghobari and Tom Finn in Sanaa; Writing by Joseph Logan; Editing by Ben Harding)