MOGADISHU, Somalia — A powerful car bomb explosion hit a busy market in the western part of Mogadishu on Sunday, killing at least 34 people and highlighting the security challenges that Somalia’s new government faces.

Somalia’s new president, Mohamed Abdulahi Mohamed, visited victims wounded by the blast and offered a $100,000 reward for information leading to the arrest of those who planned it.

‘‘It was a horrific and barbaric attack only aimed at killings civilians,’’ police Captain Mohamed Hussein said.

The blast was the first major attack since Somalia’s new president was elected on Feb. 8. Although no group had claimed responsibility, it bore the hallmarks of Somalia’s Islamic extremists rebels, Al Shabab.

A few hours before the blast, Al Shabab denounced the president as an ‘‘apostate’’ and a puppet of the United States. Mohamed is a US citizen and spent years in the United States, working as a contracting officer for the New York State Department of Transportation.

Associated Press