Al Qaeda militants killed at least two government soldiers when they ambushed a patrol in central Yemen on Wednesday, local officials said.
The attack in oil-producing Maarib province was carried out the day after at least 15 militants were killed in two attacks in southern Yemen.
"We believe that members of Al Qaeda were behind this attack," the governor of Maarib said. Tribesmen said three soldiers died in the ambush and five soldiers and several militants were wounded.
In Tuesday's attacks, a drone killed at least 12 militants in southern Yemen, and government soldiers killed three militants in a separate assault. In Sanaa, gunmen sprayed the information minister's car with bullets but he was unhurt.
In Sanaa, efforts to secure the release of six aid workers kidnapped by tribesmen in a tourist area west of the capital on Tuesday stalled over demands that a man held in jail be freed first, mediators said.
They said the hostages were being held at a house in al-Ahjar, a small town 45 minutes drive west of Sanaa, and were in good condition.
"They are in good health, there is no threat to their safety... (the kidnappers) are giving them meals," a tribesman told Reuters on Wednesday.
In Geneva, the United Nations declined to confirm the kidnapping report but said that a "crisis coordination centre" had been set up in Sanaa and New York.
"The U.N. crisis team is working in close coordination with the government of Yemen to expedite the safe and earliest release of colleagues," Elisabeth Byrs, spokeswoman of the U.N. Office for the Coordination of Humanitarian Affairs (OCHA), told Reuters in Geneva.
The state news agency Saba said the aid workers were a German, a Colombian, an Iraqi, a Palestinian and two Yemenis. A U.N. source said the six worked for OCHA.