A suicide bombing Sunday morning in the southern Yemeni port city of Aden killed at least 40 soldiers. The Islamic State group, also known as ISIS, claimed responsibility of the attack.

The bombing took place when a suicide bomber — who blended in with soldiers queuing to get their salaries — blew himself up, Col. Nasser Sarea told Agence France-Presse (AFP). The attack took place at a Yemeni coast guard installation near Aden’s Solaban military base.

"The number of those killed has exceeded 40, with some 50 others wounded," Aden health chief Abdel Nasser al-Wali told AFP, adding that the death toll was likely to go up due to "critical cases."

ISIS said more than 70 "apostates" were killed in the blast carried out by the bomber identified as Abu Hashem al-Radfani. The militant group also said the "martyrdom seeker" got through security checkpoints before the bombing.

The base was targeted by a suicide bomber Dec. 10, and that blast killed 48 soldiers and wounded 29 others. The attack was claimed by a Yemeni affiliate of ISIS.

Aden is under control of sections loyal to the internationally recognized government of President Abdrabbuh Mansour Hadi. They are fighting the Shia Houthi rebels and their allies. ISIS and al Qaeda have taken advantage of the conflict to increase their presence in southern Yemen. The conflict has claimed lives of over 7,000 people, most of them civilians, since last March.