A suicide bomber has killed a civilian and six government guards in the Somali capital, Mogadishu, where Islamists and pro-government forces are fighting. The bomber drove a pick-up truck to the gate of a military base, and detonated an explosive in front of the guards. The attack follows two weeks of intense fighting which the UN's special envoy for Somalia called a coup attempt. Ahmedou Ould-Abdallah told the BBC the Islamists knew they cannot run Somalia while the UN lists them as terrorists. Mr Ould-Abdallah warned the Islamist leaders that "to take the whole country hostage is not a solution, it is a failure". He said that if they succeeded in defeating the government it would leave "the whole population hostage to drastic sanctions, including threats to arrest [the Islamists] and bring them to justice". On Friday the government hit back at this latest action against it, attacking key rebel strongholds. Mogadishu has been blighted by 18 years of almost uninterrupted civil unrest. Rise in violence "A speeding car laden with explosives entered the camp and exploded inside," Deputy Mogadishu Governor Abdifatah Shaweye told reporters. map Four guards were killed at the scene and two more died in hospital of their injuries, a police commander told Reuters news agency. At least seven people were injured. Little is known about the bomber, but Deputy Regional Governor Abdifitah Ibrahim Shawey told the Associated Press news agency that he is believed to have been one of about 300 foreign fighters helping the insurgents. This month has seen a notable upsurge in violence in Mogadishu - with first the Islamists and then pro-government forces renewing their attacks. About 200 people are thought to have been killed since the beginning of May, at least 50 of whom have died since Friday morning. So far, most of the fighting has focused on one of the city's main routes, Wadnaha Road, according to the BBC's Mohamed Olad Hassan in Mogadishu. African Union peacekeepers based in the capital to support the fragile administration are not involved in the attacks, our correspondent says. The 4,300-strong force does not have a mandate to pursue the insurgents. A moderate Islamist President, Sheikh Sharif Sheikh Ahmed, was elected by a unity government in January as part of a UN-backed peace initiative. But even his introduction of Sharia law to the strongly Muslim country has not appeased the guerrillas, who are accused of having links with al-Qaeda. Mr Ould-Abdallah would not be drawn on the African Union request for UN sanctions against Eritrea, which is suspected of aiding the Islamists.