MOGADISHU (Reuters/AFP) - Rebels and Somalias western-backed government and allies exchanged mortar and small arms fire on Thursday in the seventh day of clashes in the capital Mogadishu that have killed 139 civilians. Years of conflict in Somalia have killed tens of thousands, displaced millions more, defied 15 attempts to establish central rule and created one of the worlds worst aid crises. Twenty-six civilians died and 98 were injured on Wednesday and Thursday, said Yasin Ali Gedi, vice chairman of the Mogadishu-based Elman Peace and Human Rights group. Thousands have also evacuated in this period, because fighting has spread to new districts, he said. The militant al Shabaab and forces loyal to President Sheikh Sharif Ahmed continued to battle in Mogadishu. Pockmarked buildings near the presidential palace shook from the latest bout of clashes, which have plagued the country since dictator Mohamed Siad Barre was ousted in 1991. Residents accused African Union peacekeepers (AMISOM) of shelling insurgent strongholds. Like most guerrilla wars, rebels stage hit-and-run attacks and hide amongst the populace. I saw them transporting 10 dead bodies and dozens of injured in mini-buses, resident Abdi Hussein said. They were all opposition, because they were masked. Government soldiers also died, but I could count only three. Im sure there are more. We were running from the shelling of AMISOM, he said. AU spokesman Barigye Ba-Hoku said: We are neither involved in fighting nor shelling. The opposition blames shelling on us as an excuse to attack our bases. Meanwhile, Somalias president was holed up in his compound and residents were fleeing Mogadishu Thursday, as hardline insurgents prepared their bid to seize power. Radical opposition leader Sheikh Hassan Dahir Aweys urged his former ally President Sharif Sheikh Ahmed to leave office, as warring factions regrouped ahead of an expected final battle. Insurgents have been redeploying forces from across the country to launch an unprecedented offensive, while Ugandan and Burundian African Union peacekeepers held the fort for Sharifs beleaguered administration. We know they have deployed many militants and are getting ready for their final attack but they will never win, Somali government security officer Colonel Ahmed Dahir told AFP in Mogadishu. Sharif, who was elected Somalias president in January and received international backing, has not been able to build up his own security forces and his authority appeared to hang by a thread after days of fighting in the capital that killed dozens and wounded hundreds. Government forces backed by AU peacekeepers controlled nothing in the capital but the presidential compound, a handful of other government institutions in adjacent buildings, and the airport and seaport, witnesses said. Residents continued to flee Thursday, fearing that a fresh insurgent onslaught would be met by a barrage of artillery fire from AU and government forces hunkering down in a last handful of fortified pockets. The International Committee of the Red Cross said in a statement that thousands of people have fled their homes in search of shelter and security over the past few days. Hardline insurgents remained determined to topple Sharifs fledgling administration despite failing to go all the way with their initial offensive last week. The insurgent forces consist mainly of the Shebab movement, a hardline group whose leaders are suspected of links to Al-Qaeda, and Hezb al-Islamiya, another armed organisation loyal to Sheikh Aweys. The purpose of this war is to protect a country and its religion from invading Christian forces and their Somali stooges. We will die for that, Shebab commander Sheikh Mohamed Ayyub told AFP.