( CNN ) -- Heavy fighting between Islamist militants and government forces in Somalia 's capital has left 18 people dead and dozens wounded , medical officials said Sunday . `` The fighting is huge and is marked by heavy exchange of artillery , '' said Ali Musa , a head of a Mogadishu ambulance service . Of the 36 reported wounded , 11 were hurt when an artillery shell hit their bus near Mogadishu 's Bakara Market . The African Union peacekeeping mission in Somalia said the fighting centered around attempts to destroy a network of tunnels and trenches that the jihadist movement Al-Shabaab used to move weapons and fighters around the capital . The dead included two peacekeepers and six rebel leaders that the Ugandan-led mission said were linked to al Qaeda . `` The discovery and closure of this tunnel is a major step forward in the stabilization effort in the city , '' the Ugandan-led AMISOM mission said in a statement issued Sunday . AMISOM said the fighting erupted Saturday as Al-Shabaab tried to retake the tunnel network . Somalia 's state-run radio network said 28 rebels were killed in Saturday 's clashes . AMISOM 's communique said foreign fighters have effectively taken over Al-Shabaab . It said five of the six rebel leaders killed in the recent fighting came from countries beyond Somalia -- Yemen , Pakistan , India , Kenya and Syria -- while the nationality of the sixth was unknown . AMISOM , which supports Somalia 's transitional government , said the combined forces now control about 60 percent of the city . But the government has little influence beyond Mogadishu , and Al-Shabaab controls much of southern Somalia . The horn of Africa nation has not had an effective government since Mohamed Siad Barre was overthrown two decades ago . Journalist Mohammed Amiin Adow contributed to this report for CNN .
Somalia : AMISOM says 5 of 6 slain rebels were non - Somalis . News crews report ` ` huge '' fire in Mogadishu . Peacekeepers report success in killing Islamist militants .