Three soldiers were killed in one attack when a suicide bomber rammed his vehicle against an army position in the southern Shabwa province town of Maifaa, one source told AFP.
Almost at the same time two other soldiers were killed in nearby Azzan village when Al-Qaeda suspects opened fire with automatic weapons at another military post, another army source said.
Witnesses said clashes erupted between the gunmen and soldiers after the Azzan attack.
Ten Al-Qaeda suspects were also killed in an exchange of fire with soldiers at the Qatan army barracks in restive Hadramawt province.
Al-Qaeda in the Arabian Peninsula, considered by Washington as the most dangerous affiliate of the jihadist network, is active across several parts of Yemen, taking advantage of a collapse of central authority during a 2011 uprising that ousted veteran president Ali Abdullah Saleh.