Four people, including a soldier, were also wounded in the fighting in the provincial capital Zinjibar on Sunday night.
On Saturday, a local official said the army killed five suspected al Qaeda militants in Zinjibar, one of whom was Iraqi and another Saudi.
Abyan has been in a state of anarchy since militants, suspected of ties to al Qaeda, began seizing cities in the coastal region several months ago. The government said it had "liberated" Zinjibar from Islamist fighters in September.
Nine months of anti-government protests have paralysed impoverished Yemen, pushing it to the brink of civil war but failing to oust President Ali Abdullah Saleh.
Vice-President Abd-Rabbu Mansour Hadi, who has been mandated by Saleh to negotiate a power transfer deal under a Gulf-brokered plan to end the crisis, returned to Yemen on Monday after undergoing "routine annual checks" at a U.S. heart hospital, officials said.
Reports in opposition media said Hadi may have visited the United States to assuage pressure on Saleh to sign the Gulf power transfer plan which would see him stand down and trigger early presidential elections. (*)
Editor: Kunto Wibisono
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