( CNN ) An improvised bomb exploded near a U.N. vehicle traveling near the northeastern Somali city of Garowe on Monday morning , killing six people -- including four aid workers for the international children 's agency UNICEF . Somalia 's President called it `` an attack against the future of our country . '' The attack follows a separate incident Sunday in which three African Union troops died in an ambush in the Lower Shabelle region of Somalia . The terrorist group Al-Shabaab claimed responsibility for Monday 's attack , which occurred about 8 a.m. in the administrative capital of the autonomous Puntland region , according to the United Nations Assistance Mission in Somalia . Four of the victims were foreigners and two were Somalis , said Ahmed Abdullahi Samatar , the police chief of Puntland . UNICEF , the U.N. aid agency focused on children , said it employed four of the dead . Four other workers were in serious condition , the agency said . The bomb went off as a vehicle was taking workers from their guest house to their office . The local police chief said the bomber was inside the vehicle among the U.N. staff . The bomber also died in the attack , according to authorities . Nick Kay , the special representative of the U.N. secretary-general for Somalia , condemned the attack on his Twitter account . `` Shocked and appalled by loss of life , '' he said . Somalia 's President , Hassan Sheikh Mohamud , said he was horrified by the attack . `` This attack is not just targeted at the United Nations , but in attacking UNICEF , Al-Shabaab has also attacked Somali children . It is an attack against the future of our country and I condemn it in the strongest possible terms , '' he said . UNICEF called the slain workers `` an integral part of UNICEF 's work in Somalia , dedicated to improving the lives of others . '' Al-Shabaab , the al Qaeda-affiliated terrorist group based in Somalia , caused outrage this month by carrying out an attack on a Kenyan university . Nearly 150 people , most of them students , died in that attack . In the Sunday incident , three African Union troops were ambushed in the Lower Shabelle region . The African Union Commission for Somalia , or AMISOM , said Sunday that the troops died during a `` spirited fight '' with attackers . `` This attack on AMISOM peacekeepers is part of the continuous effort to subvert Somalia . It is an attempt at disrupting the growth that is evident across all regions , by the enemies of the Somali people . The blood of our brothers will however not be shed in vain . AMISOM will remain committed to pacifying Somalia , '' said AMISOM Ambassador Maman S. Sidikou . CNN 's Nana Karikari-apau and journalist Omar Nor contributed to this report .
The bombing is `` an attack against the future of our country , '' Somalia 's President says . UNICEF says the staff members ' vehicle was hit by an explosion on its way to their office . Four wounded staff members are in serious condition , the agency says .