An explosion was heard Saturday in the Somali capital, scene of frequent attacks by Islamic extremist fighters.

Witnesses said the blast was heard near the headquarters of the Somali intelligence agency in Mogadishu.

Somali police didn't immediately provide more information.

The Somali Islamic extremist group al-Shabab frequently carries out suicide bombings targeting public places and government offices. Hotels and restaurants are also attacked.

The al-Qaida-linked al-Shabab, Africa's most active Islamic extremist group, has been fighting for years to take power and create an Islamic state in the Horn of Africa nation.

The group has carried out many attacks in neighboring Kenya in retaliation over Kenya's deployment in 2011 of peacekeepers in Somalia.

Al-Shabab continues to mount lethal attacks despite being pushed out of Mogadishu. It mostly operates from rural areas in the country's south.

The U.S. military has carried out a number of deadly airstrikes in recent months against al-Shabab.