A mortar and machine gun battle in north Yemen drew in government forces overnight, killing at least 19 people and complicating efforts to cement a truce, local officials said.
The battle was between Shi'ite rebels and pro-government tribesmen.
"Yesterday night there were very violent confrontations. Nine soldiers and pro-government tribesmen were killed as well as about 10 Houthis (rebels)," a local official in the flashpoint Harf Sufyan region told Reuters today.
"It remains very tense after the failure of efforts to stop the fighting between the two sides," he added.
Separately, gunmen killed at least five Yemeni soldiers in an ambush on a military convoy in south Yemen.
Al Qaeda was suspected of being behind the attack, a provincial official said.
"There was an ambush targeting the soldiers' vehicle and five were killed and a sixth was wounded. There is suspicion that al Qaeda was behind the operation," the official in the southern province of Shabwa said.
