Fourteen people were killed when two car suicide bombers struck the entrance of a military base and a checkpoint near the headquarters of the Southern Transitional Council in Aden on Saturday.
Some 40 people were also injured when the bombers blew up their vehicles in the Gold Mohur area of Aden's Al Tawahi district at 5.20pm. The death toll included a member of Aden's elite counter-terrorism forces, a woman and two children, according to officials.
Two other attackers wearing explosive belts also tried to climb over the external gate of the military base to reach the inside but were shot dead by guards before they could blow themselves up.
ISIL claimed responsibility in a statement carried by its Amaq news agency.
Local shops and houses were severely damaged in the attack while the force of the blasts shattered windows in the headquarters of the STC, which is calling for an independent southern Yemen.
The southern port city is also home to the internationally recognised government of Yemeni president Abdrabu Mansur Hadi. Mr Hadi's government was forced to flee there after the Houthi rebels captured the capital, Sanaa, in September 2014.
Pro-Hadi forces — backed by a Saudi-led military coalition — are fighting the Houthi rebels and allied fighters for full control of the country. Extremist groups, including local affiliates of Al Qaeda and ISIL, have taken advantage of the conflict to expand their presence in southern Yemen.
An estimated 46 Houthis were killed in Saudi-led coalition air strikes on rebel targets along Yemen's Red Sea Coast, UAE state news agency Wam reported on Saturday, citing Yemeni military sources.
The UAE is a leading member of the coalition.
The targets struck included farms used by the Houthis east of the area of Al Jarahi, as well as rebel vehicles carrying reinforcements to the militants in Al Jarahi.
The coalition strikes came after five missiles fired by the rebels at pro-government positions on Friday were intercepted.
The Houthis fired the missiles at pro-government troops near the city of Marib, but all were shot down by the air defence network operated by the coalition, Khaled Al Karni, a journalist working for the Yemeni army, told The National.
Marib city lies 173 kilometres to the north-east of Sanaa, the Houthi-held Yemeni capital.
The missiles were fired after pro-government forces, backed by the coalition, pushed back an offensive by the Houthis.
The aim had been to take back control of military sites in the Serwah area of Marib province that were liberated by the army last week.
But the Houthi offensive failed as government troops repelled the militants who tried to break into the area.
Houthi rebels besieged Marib for months in 2015 after capturing Sanaa but they were pushed back in fierce clashes with local tribesmen aided by the coalition.
Marib faces the constant threat of Houthi rockets, hundreds of which have been launched toward the city.