At least 13 pro-government fighters were killed and tens of others injured in an ambush by the Houthi militants in Yemen's province of Taiz on Monday.
Military sources told the Yemen Post that the Houthis fired missiles against the pro-government fighters, who were deployed as reinforcements to back the forces to retake Taiz while passing in the town of Dhubab on the Red Sea.
Fierce battles erupted between the pro-government and Houthi fighters after the ambush in which around 32 Houthis were killed and others injured, the sources said.
The reinforcements were dispatched from the south for the offensive to drive the Houthis out of Taiz.
They have already arrived in the province, they said.
The government forces with support from the Saudi-led coalition launched the offensive early Monday.
Reinforcements including Arab troops and heavy equipment were deployed through the southern and western gates of Taiz for this offensive, chief of the fourth military command told TVs.
Separately, local news websites reported that 15 pro-government fighters, known as popular resistance, were killed after their vehicle was bombed on the border between Taiz and Lahj.
Others were injured in the incident, reports said.