Yemeni forces say they have driven Al-Qaeda militants from a key mountain stronghold in the province of Abyan, in the latest victory against the terrorist group.

Military units commanded by the pro-independence Southern Transitional Council on Thursday pushed deep into Omaran valley to strike a blow against the group’s decade-long occupation, Mohammed Al-Naqeeb, the STC’s spokesman said.

“They tried to stop our forces’ advance into the valley by deploying snipers, planting IEDs (improvised explosive devices) and blowing up bridges and roads,” he said.

Yemeni forces “cautiously” pushed into the valley as other troops blocked the entrances to catch fleeing militants, he added.

One soldier was killed and four were injured when the militants counterattacked and detonated 15 IEDs, he said.

Despite the stiff resistance, local officials now say nearly 80 percent of Abyan has been cleared of Al-Qaeda.

STC forces also took control of an area called Al-Mousinah in neighbouring Shabwa province, the spokesman said.

Al-Qaeda announced on social media that it would launch a counteroffensive called “Truth Arrows,” while also denying it had suffered setbacks in Abyan and Shabwa.

Yemeni terrorism expert Saeed Obeid Al-Jemhi described the STC operation in Omaran valley as a major blow to Al-Qaeda. 

“This valley is an important stronghold for the organization and may be one of its last safe strongholds. It hasn’t been attacked by ground forces like this until recently,” he said.

Omaran has long served as a remote haven for Al-Qaeda. The group has run numerous training centers, recruitment hubs and workshops for making IEDs and other weapons, local officials said. 

The operations on Thursday are part of the STC’s “Eastern Arrows” offensive to drive out Al-Qaeda following a series of deadly attacks and kidnappings in Yemen’s southern provinces.