A gunman opened fire on a U.S. security team that was training Yemeni soldiers in the south of the country, the Pentagon and a local security official said on Friday, both denying reports from an Islamist group that a CIA officer was killed in the assault.

In the north of the country, meanwhile, a bomb blast hit an anti-U.S. protest, injuring at least 22 people, according to a rebel group that controls much of the region.

Fighting with northern Houthi rebels and southern militants are among the challenges facing Yemen’s new president, Abd-Rabbu Mansour Hadi, a man Washington was hoping could end a year of turmoil in the country.

Ansar al-Sharia, a Yemen-based Islamist group linked to al-Qaeda, said it had attacked and killed a U.S. officer in the south on Thursday.

“The mujihadeen killed a CIA officer on Thursday while he was in Aden province, after tracking him and determining he was cooperating with the Sanaa government,” it said in a text message sent to journalists in Yemen.

A Yemeni security official in Aden, speaking on the condition of anonymity, said a gunman fired on a U.S. security team on Thursday, but the shots had hit their armored vehicle without injuring anyone.

In Washington, a Pentagon spokesman confirmed that a gunman fired several shots at an armored vehicle carrying a U.S. security team in Yemen and said that no one was wounded.

Fears that political turmoil in Yemen would embolden al-Qaeda’s wing in the country led Washington and Gulf Arab states to broker the exit of Hadi’s predecessor, Ali Abdullah Saleh, after a year of mass protests against his rule.

Saleh’s departure made him the fourth Arab leader to be removed from power since mass uprisings swept east from Tunisia in late 2010, rattling U.S. allies and foes alike.

Hadi, who won a one-candidate election to replace Saleh last week, has promised to lead Yemen to new elections, create a new constitution and reform the military within two years.

He inherits multiple conflicts, including clashes with secessionists in the south and the long-simmering insurgency in the north.

Islamist militants took control of swathes of territory in southern Yemen during the struggle over Saleh’s fate, and they hold the city of Zinjibar in southern Abyan province.

The bomb that exploded during a protest against U.S. involvement in Yemen injured 22 people in the north, according to the leader of Shiite Muslim rebels who control the area. In a statement, the leader of the Houthi movement — Shiite rebels whom Yemen’s military tried to crush in campaigns in 2004-2009 — blamed the U.S. ambassador in the capital, Sanaa, for the explosion in Saada, near the Saudi border.

The region has been the site of fighting recently between the Houthis and Sunni Muslims espousing puritanical Salafi doctrines that are influential in Saudi Arabia and cast Shiites as heretics. The Houthis have accused Riyadh of arming their foes.

Southern secessionists have rejected the transition deal that put Hadi in power, saying they want northing to do with a process involving a united Yemen.

In Sanaa, thousands of protesters gathered near Hadi’s residence, demanding that the military be shaken up to exclude Saleh’s relatives and loyalists, witnesses said.

— Reuters