A Somali soldier stands guard near destroyed shops after a car bomb blast close to the Somali government's headquarters. (Farah Abdi Warsameh/AP)

A suicide bomber driving a car filled with explosives killed at least 10 people in the Somali capital of Mogadishu on Monday, illuminating the lingering security challenges faced by the U.S.- and U.N.-backed government.

Somalia’s al-Qaeda-linked militia, al-Shabab, claimed responsibility for the attack, the deadliest this year in Mogadishu. The militia continues to stage guerrilla assaults, more than a year after African Union peacekeepers pushed the militants out of the capital.

The bombing appeared to target a group of Somali government officials, including Mogadishu’s security chief, near the presidential palace, but instead struck a minivan filled with passengers, according to police and witnesses. The attack occurred on a main road, lined with shops and tearooms, between the palace and the national theater.

“The suicide car bomber targeted a senior national security officer whose car was passing near the theater,” senior police officer Abdiqadir Mohamud told Reuters, adding that the official was injured and that most of the people who died were civilians on the minibus. “This public vehicle coincidentally came between the government car and the car bomb when it was hit. Littered at the scene are human hands and flesh,” the news agency reported.

Sheik Ali Mohamud Rage, a spokesman for al-Shabab, told Reuters that the attack was revenge for the deaths of its members targeted by the Somali national security forces. The militia still controls large swaths of rural Somalia, even as it has been pushed out of major cities, including the Indian Ocean port city of Kismayo, which has severely damaged its ability to raise money.

Since late 2011, security in Mogadishu has improved considerably, prompting the United Nations and some countries to reopen offices and embassies in the capital. A nearly 18,000-strong African Union force still protects the fragile central government.

Nevertheless, Monday’s bombing was a reminder of the militia’s ability to create havoc and disrupt efforts by Somali President Hassan Sheik Mohamud to pull the nation out of more than two decades of civil war. Mohamud was elected last year in Somalia’s first nationwide vote since the fall of dictator Siad Barre in 1991, an event that helped trigger the country’s descent into turmoil.