Yemeni fighters allied with exiled President Abd-rabbo Mansour Hadi killed 15 rebels in a Thursday attack on their checkpoints in the country's southern Abyan province, a military source said.
In second city Aden, 17 rebels were killed in air strikes by Saudi-led coalition warplanes, according to pro-Hadi military sources.
Fighters belonging to the pro-government Popular Resistance Committees in Abyan's Zinjibar attacked checkpoints of the 15th Infantry Brigade, which has defected and joined Iran-backed Shia Houthi rebels, the military source said.
The southern fighters also besieged the headquarters of the brigade, which was later hit by warplanes from the coalition that launched an air campaign in March backing Hadi.
Southern tribesmen meanwhile killed four Houthi rebels in an ambush Thursday near Ataq, in Shabwa province, a local security source said.
Troops loyal to former president Ali Abdullah Saleh have sided with the Houthis, who overran the capital in September and went on to seize control of several regions.
The rebels forced Hadi into exile when they advanced in March on the port city of Aden, where he had taken refuge after escaping house arrest in Sanaa.
Aden's health chief Al-Khader Laswar said 19 civilians, including three children and a woman, were killed and 115 others wounded since Tuesday in rebel rocket attacks on the city.
AFP could not confirm the tolls from medical sources.
The UN says more than 3,200 people have been killed and 1.26 million displaced in Yemen since fighting broke out in March.