At least six Yemeni troops were killed and dozens were wounded on Wednesday when two suicide bombers blew up their cars at a military base in the southern city of Aden, security sources said.

About two dozen militants launched an attack on the soldiers inside the base after the explosions. Gun battles at the base, in the Khor Maksar district, were going on and military reinforcements were arriving, the sources said.

The attacks followed bombings in three Saudi cities on Monday, after days of mass killings in attacks in Turkey, Bangladesh and Iraq apparently by the Islamic State group as the Islamic holy month of Ramadan draws to a close.

Islamist militants have gained territory and freedom to operate in Yemen thanks to a war raging for more than a year in which government forces have been pitted against Iran-allied Houthi rebels who control the capital, Sanaa.

Yemeni security officials believe there is an overlap between adherents of al Qaeda and Islamic State, though the two groups are ideological rivals and compete for recruits.

Al Qaeda has used the security vacuum to seize control over swathes of southern and eastern Yemen, while Islamic State has launched several mass-casualty attacks on security forces.

Three coordinated Islamic State bomb attacks on government troops killed 38 people in the southern port city of Mukalla on June 27 as they were preparing to break their dawn-to-dusk fast during Ramadan.