Thirteen people, including seven Yemeni soldiers and three separatists, were killed in a gun battle Tuesday in the city of Daleh, the latest violence to hit the country's volatile south.
A military official said gunmen ambushed an army convoy near the office of the local government in Daleh with anti-tank rockets and automatic rifles.
Defence ministry news website 26sep.net confirmed the attack, saying it killed "seven soldiers, including an officer" and wounded nine others.
The official had earlier give a toll of five killed and eight wounded.
A southern activist said three of his comrades died in the fighting and that 20 people were wounded, mostly civilians.
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The activist said militants torched a military vehicle and captured 15 soldiers during the confrontation, after three others were taken hostage in a clash on Monday.
State news agency Saba reported that authorities have arrested 21 "saboteurs."
Separatists in the formerly independent south boycotted a national dialogue that agreed last month to transform Yemen into a federation in a bid to address local grievances that have fuelled unrest across the Arab world's poorest country.
South Yemen was independent between the end of British colonial rule in 1967 and its union with the north in 1990.
Support for renewed independence in south Yemen runs deep in Daleh.