At least 15 people are dead after a suicide car bomber posing as a milk delivery van detonated at a district headquarters in Somalia's capital, police said Tuesday.

The death toll may rise, as some of the at least nine people wounded were badly hurt in the explosion at Wadajir district headquarters in Mogadishu, Capt. Mohamed Hussein told The Associated Press.

Most of the dead were civilians, Hussein said.

The al-Qaida-linked al-Shabab extremist group quickly claimed responsibility for the attack via its Shahada News Agency, according to the SITE Intelligence Group, which monitors jihadist groups.

The blast comes less than a week after al-Shabab gunmen carried out an overnight siege on a popular restaurant in the Somali capital, killing at least 31 people.

The Somalia-based al-Shabab often targets high-profile areas of Mogadishu, including hotels, military checkpoints and areas near the presidential palace. It has vowed to step up attacks after the recently elected government launched a new military offensive against it.

Al-Shabab last year became the deadliest Islamic extremist group in Africa, with more than 4,200 people killed in 2016, according to the Washington-based Africa Center for Strategic Studies.

The extremist group also faces a new military push from the United States after President Donald Trump approved expanded operations, including airstrikes, against al-Shabab.