Unlike previous attacks by al-Shabab, which is linked to al-Qaida, gunmen did not accompany the suicide bomber, said police Capt. Mohamed Hussein. The first suicide car bomber tried to speed through the barrier at the U.N. office but guards shot at the car, he said. A second suicide blast targeted a checkpoint manned by Somali security forces near the African Union base in Mogadishu, said Hussein. Casualties there remain unclear.