Eight militants and four Yemeni soldiers were killed in clashes Thursday, local officials and medics said, near a southern provincial capital seized by Islamist dissidents in May.
The twelve militants and soldiers were killed in the suburbs of Zinjibar, in Abyan province where the militants have seized several towns, while 11 months of protests against President Ali Abdullah Saleh have pushed Yemen to the brink of civil war.
The bodies of the five soldiers and those of some of the dead armed men have been moved to Aden's medical hospital, a medic told Reuters in the southern port city.
The government says the militants are linked al Qaeda's Yemen-based regional wing, which the United States has called the most dangerous branch of the militant network.
Saleh's opponents have accused him of ceding territory to Islamists to bolster his assertion that his rule keeps al Qaeda in check.
Neighbouring oil giant Saudi Arabia and Washington fear that continued unrest in Yemen may embolden its al Qaeda wing, which has claimed responsibility for operations that include a failed plot to blow up a U.S.-bound passenger plane in 2009.
In Sanaa, Hamid al-Ahmar -- a tribal leader, wealthy businessman and a member of the Islamist opposition party Islah -- called for Saleh to be put on trial, opposing any move to grant him immunity under a transition deal aiming to end nearly a year of unrest in the poor Arabian Peninsula country.
The government's proposed immunity for Saleh is tantamount to neglecting the blood of the Yemeni people, Ahmar said in a statement, referring to the hundreds killed during the protests.
Ahmar called for Saleh to be charged, echoing a demand raised by demonstrators across Yemen since the transition deal sponsored by the Gulf Arab states was signed in November to end Saleh's 33-year rule.
Separately, Yemen's transport minister told Reuters on Thursday Sanaa would renegotiate a joint venture agreement with DP World to run the Aden container port, accusing the Dubai-based operator of failing to fulfil its obligations.
(Reporting by Mohammed Mukhashaf in Aden and Mohammed Ghobari in Sanaa; Writing by Firouz Sedarat; Editing by Matthew Jones)