The African Union's envoy to Somalia said on Monday that the organisation would increase its troops in the country to 8,000 from the current 3,500, despite Sunday's attack on an AU base in Mogadishu which killed 11 Burundian soldiers.
Nicolas Bwakira told a news conference at the AU HQ in Nairobi, Kenya, that several countries "have indicated their commitment to contribute additional troops".
Bwakira said Somali President Sheik Sharif Sheik Ahmed had asked the African Union to continue to support his government and boost the number of peacekeeping troops.
An extremist Islamist group called al-Shabab claimed responsibility for Sunday's attack, the deadliest on African Union forces during the two-year deployment in Somalia.
An African Union official said on Monday that the suicide bomber was a Somali contractor who delivered supplies and had easy access to the base.
Bwakira said 22 soldiers have been killed in Somalia to date.
The AU's Peace and Security Council met in the Ethiopian capital in an emergency session for three hours on Monday but its deliberations were closed to reporters.
The AU peacekeeping force has a restricted mandate to guard key government installations in Mogadishu.
It has not been involved in fighting Islamist militants in the capital, battles that have killed thousands of civilians over the past two years.
But hardline groups still view the peacekeepers as an occupying force.
Al-Shabab has threatened to focus attacks on African Union troops, now that Ethiopian forces have left Mogadishu after two years.
The US State Department considers al-Shabab a "terrorist" organisation linked to al-Qaeda, something the group has denied.
The Somali government controls virtually no territory.