SANAA, Yemen — A huge explosion killed the governor of Yemen’s southern Aden province and six of his bodyguards on Sunday, security officials said, in an attack that was later claimed by a local Islamic State affiliate.

Gov. Gaafar Mohamed Saad was traveling to his office when the explosion struck his convoy in the southern port city. Authorities are investigating the exact cause of the explosion. The officials spoke on condition of anonymity because they were not authorized to brief the media.

An Islamic State affiliate claimed the attack in a statement circulated online by supporters, saying the bomb was concealed in a parked car along the convoy’s route. The group referred to Saad as a “tyrant” and warned the “heads of the infidels” in Yemen that it would carry out “operations to chop off their rotten heads.”

Islamic State, also known as ISIS or ISIL, has claimed a series of bombings that killed 159 people and wounded 345 this year in Yemen, according to an AP count.

The extremists have been able to expand their reach in the chaos of Yemen’s larger conflict, between a loose array of pro-government forces backed by a Saudi-led coalition and Shiite Houthi rebels, who control the capital, Sanaa, and large parts of northern Yemen. Pro-government forces drove the Houthis out of Aden earlier this year.

A local al-Qaida affiliate has exploited the chaos to seize territory in Yemen’s south and east, and has a growing presence in Aden. On Saturday, masked gunmen in Aden killed a military intelligence official and a judge known for sentencing al-Qaida militants. No one claimed those attacks.

The United Arab Emirates’ minister of state for foreign affairs, Anwar Gargash, condemned the killing of the Aden governor and described the perpetrators as “treacherous terrorists.”

“These crimes will not discourage our common resolve to restore security and stability throughout the brotherly nation of Yemen,” he said in a statement carried by state news agency WAM.

The seven-state Emirates federation and neighboring Saudi Arabia are leading a coalition backing the internationally recognized government. The Emirati military has played a key role in helping to secure Aden.

The Emirates also has been outspoken against the Islamic State group and is part of the U.S.-led coalition fighting the group in Iraq and Syria.