Yemen tanks and troops moved against an Al Qaeda stronghold, on Monday.
Al Qaeda was holding hostages in the town of al-Bayda, and negotiations had collapsed.
In an apparent retaliation, a suicide bomber hit a military checkpoint, in Radda.
Eleven Yemeni soldiers were killed and another seventeen were wounded, in the blast.
A separate attack, near Radda, launched by gunmen, killed three Yemeni troops, who were on patrol.
Many southern towns were taken by Al Qaeda, in 2011.
Since then Yemen, backed by the US, has worked to remove them.