The African Union says 21 people were killed in Somalia during suicide bomb attacks on AU forces at its main base in the country.
Gaffel Nkolokosa, a spokesman for the AU's Somalia mission says 17 peacekeepers, including five Ugandans and 12 Burundians and four civilians were killed Thursday when two car bombs exploded at the base in the Somali capital, Mogadishu.
Burundian General Juvenal Niyoyunguruza was among those who died in the attack.
The spokesman says 40 others were injured including the Ugandan general Nathan Mugisha that heads of the force. Many wounded have been evacuated to Kenya for treatment.
The Islamist militant group al-Shabab claimed responsibility for the attack. The group said it was retaliation for Monday's U.S. helicopter raid that killed an al-Qaida-linked terrorist suspect Saleh Ali Saleh Nabhan in southern Somalia.
Witnesses say the blasts were caused by two vehicles with United Nations markings that guards had allowed into the AU compound.
AU Commission Chairman Jean Ping strongly condemned the attack, saying it was carried out by terrorist elements determined to undermine recent progress in Somalia.
Thursday's incident was the deadliest attack against AU forces since suicide bombers killed 11 Burundian soldiers in February.
About 4,000 AU peacekeepers are in Somalia helping to defend the government against insurgents who want to set up an Islamic state. The peacekeepers mainly guard key sites such as Mogadishu's airport, seaport and the presidential palace.
The United States considers al-Shabab a terrorist organization and has accused it of having links to al-Qaida.
U.S. officials have expressed concern that if al-Shabab takes control of Somalia, it could turn the country into a haven for terrorists.
Some information for this report was provided by AP and Reuters.