Five hundred al Qaeda militants and 40 soldiers have been killed since the military launched an offensive against the group in April, Yemeni army spokesman, Colonel Saeed al-Faquih, told a news conference on Thursday.
Yemen's military mounted a campaign in the south of the country to try to crush the Islamist group that has killed hundreds of people, and in response the militants have stepped up attacks on government facilities after being driven out of strongholds in the southern Shabwa and Abyan provinces, Reuters reported.
They have fled to the desert and the mountains from where they have been attacking army and government targets.
"I want to stress that the military operations will also include the areas where some militants have fled and where sabotage is taking place, which is the other face of terrorism," Faquih said, noting that there were preparations taking place in Maarib province for a major assault.
As well as those killed, 39 suspected militants were under arrest, he said.
Militants from al Qaeda in the Arabian Peninsula (AQAP) and allies in its local Ansar al-Sharia affiliate fled to the mountains in the south in 2012 after Yemen's army, backed by the United States, drove them out of cities they had seized in 2011.
The insurgents have posed a challenge to government efforts to restore stability to the country since long-ruling president Ali Abdullah Saleh was forced to step down in 2012 after months of pro-democracy protests.
As well as the al Qaeda threat, the country faces challenges from separatists in the south and an emboldened Shi'ite tribal militia trying to cement its control of the northern highlands.