At least three soldiers were killed in clashes with al Qaeda militants in southern Yemen in an operation launched by the internationally recognized government of President Abd-Rabu Mansour Hadi, security sources said. At least 15 jihadists have been killed, they added.

They said at least 10 other soldiers were wounded when troops were ambushed east of the coastal city of Shuqra on Tuesday. Intense clashes were continuing on Wednesday.

The fighting began when troops backed by a Saudi-led coalition attacked an al-Qaida stronghold in the Marakasha Mountains in Abyan province, east of the southern city of Aden.

The area has long been a militant haven, attracting fighters in the 1990s returning from Afghanistan after fighting the Soviets. Al-Qaida later said in a statement circulated online that it had “ambushed” the troops and fought them off, the U.S.-based SITE Intelligence Group said.

The incident highlighted the obstacles facing Hadi’s government as it struggles to wipe out al Qaeda while simultaneously trying to defeat Houthi fighters in a war that has lasted nearly two years and killed more than 10,000 people.

In August, the Yemeni army drove al Qaeda out of two strongholds in the same region in a campaign in which at least 40 militants were killed.

The United States, which sees Al-Qaida in the Arabian Peninsula as a threat to its own security, said last month it had killed 28 militants in nine strikes in the Arab country since September.

The group has exploited the civil war between Hadi’s Saudi-backed government and the Houthis, aligned with Iran, to recruit followers and expand its influence across the country, especially in the south and east.

The impoverished country overlooks key shipping routes and shares a long border with Saudi Arabia, the world’s top oil exporter.

In other parts of Yemen, clashes were reported between Hadi supporters and fighters from the Houthi group and their allies in the southwestern city of Taiz, the northern province of Saada and in Shabwa in the southeast.