At least 17 people were killed and scores more were injured on Monday in a shootout between opposing government security forces in the capital Mogadishu, police and witnesses said.

The firefight erupted after Somali government troops killed a soldier in civilian clothes after they found a pistol on him and shot him dead. The killing triggered retaliatory attacks from other units, Omar Dahir, a police officer, told Xinhua.

"Twelve people died and as many as 20 others got injured after machine gunfire hit a crowded place near a hospital," the police officer has said. However, local media and hospital sources put the figure higher, saying at least 17 people have lost their lives.

The injured, most of them seriously, were taken to a nearby Chinese-built Banadir Hospital where they were treated.

Witnesses speak of shocking scenes as people were caught in the shootout. Body parts lay scattered in the street where the shooting happened, they reported.

"There was blood streaming all around. Limps strewn all over the place and people were screaming for help as the shooting continued and no one could help," Fadumo Osman, an eyewitness at the scene, told Xinhua.

The incident occurred in the government-controlled part of the capital Mogadishu, where government forces exercise high alert as they engage in constant battle with Islamist fighters on a daily bases.

Such clashes between units of government forces often take place in residential areas after army units mistake each other for insurgents or over differences.

Somalia, which has not had a functioning central government since 1991, has been torn apart by decades of conflict and factional strife, more recently with al-Shabaab Islamic militants.

The country is also facing a dire humanitarian crisis in which 3.2 million people, or more than 40 percent of the population, are in need of aid. Last month, the United Nations warned that a predicted drought is likely to push many more people into crisis.