Six explosions have hit the Somali capital, Mogadishu, seriously injuring six civilians - a day after Ugandan peacekeepers left for Somalia.
Civilians are often injured in mortar attacks that have hit Mogadishu
Two children were among those injured in a market where some of the mortars exploded during Friday prayers.
Dozens have been killed by insurgents since the Ethiopian-backed government forces defeated Islamists last year.
The African Union is planning to send 8,000 peacekeepers to Somalia, but has only raised half the number required.
Somalia enjoyed a six-month lull in the insecurity that has dogged the country for the last 16 years when the Union of Islamic Courts (UIC) was in power.
But violence has escalated in the past two months.
The BBC's Mohammed Olad Hassan in Mogadishu says many people were in the mosques when the explosions took place.
Mogadishu seaport and the central prison were also hit during the midday attacks, but no prisoners escaped.
The government says some 3,500 remnants of the Islamists are responsible for the escalating violence in the capital.
More than 10,000 civilians have fled Mogadishu in the past two weeks, the United Nations estimates.
An advance team of AU troops reportedly arrived in Baidoa in southern Somalia on Thursday.
The first batch of 1,700 Ugandan soldiers are expected in Somalia via sea and air next week.
When President Yoweri Museveni bade farewell to his soldiers on Thursday he said their mission was not to disarm militias, but support the government.
Nigeria has said it will start deploying its 850 troops in the middle of April. Burundi, Ghana and Malawi have also pledged to send soldiers for the mission.
There have been several protests against the deployment of AU forces in Somalia, even though many Somalis are keen to see the departure of Ethiopian forces as quickly as possible.
An insurgent group calling itself the Popular Resistance Movement in the Land of Two Migrations has threatened to wage war against the AU troops.