Nairobi/Mogadishu - The African Union's special representative for Somalia Nicolas Bwakira on Thursday condemned a roadside bomb attack that killed an AU peacekeeper in the Somali capital Mogadishu.

Two bombs exploded near Mogadishu airport on Wednesday, killing one peacekeeper and injuring another three.

Bwakira said that the attack, which he blamed on main insurgent group al-Shabaab, would not "derail" the AU's role in Somalia.

The attack on the peacekeepers came amid renewed fighting between al-Shabaab and authorities trying to bring security to Mogadishu as new President Sheikh Sharif Sheikh Ahmed returned to the capital to form a unity government.

The Elman Peace and Human Rights group said that almost 50 civilians have died since Tuesday. Over ten insurgents and around six police are also believed to have been killed in the fighting.

Sheikh Sharif, a moderate Islamist, was elected earlier this year and there are hopes that he can bring an end to the chaos that has blighted Somalia since the 1991 ouster of dictator Mohamed Siad Barre.

The new president's biggest challenge is bringing al-Shabaab into the peace process.

The insurgents have been fighting since Ethiopian forces invaded in late 2006 to help kick out the ruling Islamic Courts' Union (ICU), which was headed up by Sheik Sharif.

Over 15,000 civilians have died and over a million have fled the insurgency.

Ethiopia quit Somalia earlier this year, but al-Shabaab says it will continue fighting and accuses Sheikh Sharif of selling out to the West.

However, Sheikh Sharif is expected to rule based on Islamic law, something analysts say could undermine al-Shabaab's claim that only through force of arms can an Islamist regime come to power.

The US believes al-Shabaab has strong links to al-Qaeda, and reports emerged Thursday that Osama bin Laden had released an audio tape calling on Somalis to fight Sheikh Sharif's regime. (dpa)