Five soldiers and three militants were killed Monday during an attack on an army position in southern Yemen in which the assailants also abducted four troops, a military source said.
According to the source, the attack was carried out by southern secessionists, but secessionist leaders denied the accusation.
Southern Yemen is also home to a powerful Al-Qaeda affiliate suspected of carrying out a string of attacks on security forces.
"Attackers from the Southern Movement armed with automatic rifles and anti-tank rockets launched the attack, destroying two tanks and killing five soldiers," the military official told AFP on condition of anonymity.
"The assailants lost three men but they managed to abduct four soldiers."
Leaders of the Southern Movement denied the group was involved.
Tensions have soared in southern Yemen following deadly clashes a week ago in which secessionists stormed a governor's office to raise the flag of the former South Yemen. The fighting left two policemen and a civilian dead.
On Friday the army shelled a funeral tent for the deceased, killing 19 people, including four children, according to activists and medical sources.
After British colonial rule ended in 1967, southern Yemen was independent until union with the north in 1990.
A secession attempt four years later sparked a brief but bloody civil war that ended with northern forces taking over the south.
Southern grievances have hindered the political transition following the 33-year rule of Ali Abdullah Saleh, who stepped down last year following Arab Spring-inspired protests.
Security forces in the south have also come under repeated attack by Al-Qaeda in the Arabian Peninsula, which is among the most potent of the global terror network's franchises despite repeated Yemeni military operations and US drone strikes.