Militants killed 18 soldiers and eight police officers in south Yemen Friday morning, security officials said.
The attacks targeted installations in Shabwa province on Friday morning, the officials said. They said the attackers used car bombs and heavy artillery.
There was no immediate claim of responsibility but officials at the Defense Ministry and in Shabwa said think al Qaeda was behind the violence.
"Though no one has claimed responsibility, the planning, timing and weapons used in the Shabwa attacks give us a strong indication that al Qaeda stands behind todays attacks," a Defense Ministry official said on condition of anonymity because he is not authorized to talk to media.
"All three attacks took place within an hour in three different locations. Only an organized network like al Qaeda could stand behind such attacks."
The attacks are likely in retaliation for recent U.S. drone strikes, one security official said.
Twelve soldiers were killed at the Rothom district military compound, and six soldiers died in an attack near Mayfah district, the officials said. The Defense Ministry said a commander, Col. Nasser Tahih, was among those killed.
A raid on a police compound in Azzan killed eight officers, the officials said. Azzan is suspected to be home for hundreds of al-Qaeda militants.
In the Azzan attack, "the militants took control of the compound and looted many of its belongings and property. Those who tried to fight the militants were killed," one local security official told CNN. He spoke on condition of anonymity because he is not authorized to talk to news media.
The official said other officers surrendered to the militants and were taken prisoner.
At least nine explosions were heard at the compound, one of the officials said. No militants were known to have died in the attack, security sources in Azzan told CNN.
The government deployed hundreds of troops to the area and tight security checkpoints were introduced. Earlier this week, Yemen's Interior Ministry called for tightened security and warned that al Qaeda might be planning attacks and suicide bombings.