Another four soldiers who were wounded in the latest clashes in the city of Zinjibar were in "serious condition," said the medic at a military hospital in Aden.

A local official said street gunfights were ongoing in the city, which is partly held by militants, mainly in the neighbourhood of Bajidar.

On Sunday, security officials said that at least 25 soldiers were killed in a "friendly fire" incident and clashes with the Qaeda-linked militants.

The officials said some of the soldiers were killed in the strike by Yemen's air force in Zinjibar, although this was denied by an unnamed military official cited by state television.

Al Qaeda in the Arabian Peninsula, or AQAP, has taken advantage of nearly nine months of sweeping unrest against President Ali Abdullah Saleh to bolster its presence in the restive south and east Yemen, launching regular attacks.