Twin suicide bomb attacks hit security buildings in Yemen's Aden
The United States, which considers AQAP the most dangerous branch of al-Qaeda, also regularly conducts drone strikes on southern Yemen.
Yemen's conflict escalated in 2015 when a Saudi-led coalition launched a military intervention aimed at rolling back Houthi gains and restoring Hadi to power.
The fighting has caused a humanitarian catastrophe which the UN says is the world's worst, pushing seven million people to the brink of famine and sparking a cholera outbreak that the World Health Organisation says has killed 2,000 people.
More than 10,000 civilians have been killed in the conflict and thousands more have been injured.
Yemen is today split in two, with the Houthi-Saleh camp controlling the north and coalition-backed pro-government forces in the south.