A convoy of the African Union's (AU) AMISOM force has been targeted by a car bomb just outside the Somali capital, witnesses and a Somali army source have said, though it was not immediately clear if there were any casualties.
A spokesman for al-Shabab told the AFP news agency that the group carried out Monday's attack, saying it killed seven people, including three foreigners.
The attack took place near a checkpoint on the road linking Mogadishu and the town of Afgoye, "where a suicide bomber rammed his car into an AMISOM convoy," witness Abdulahi Mohamed said.
"There was a heavy explosion at the Alamada area ... we don't know about the casualties but I saw military ambulances rushing to the scene."
A Somali military official, Omar Adan, confirmed the attack, but declined to give the number of casualties. He however blamed al-Shabab fighters.
"Al-Qaeda linked militants, who have lost ground, are attempting desperate attacks," Adan said.
Regular deadly attacks
On Saturday, a car bomb went off in central Mogadishu near a hotel popular with government officials and businessmen, injuring at least one person, though no claims were made for the attack.
In February alone, major attacks in the capital have included a car bomb at the gates of the airport, a suicide attack on the presidential palace and a car bombing on a cafe close to the intelligence headquarters, AFp reports.
Al-Shabab fighters once controlled most of southern and central Somalia, but withdrew from fixed positions in Mogadishu two years ago.
However, the group stages regular deadly attacks in the capital, and also claimed responsibility for last year's attack in neighbouring Kenya, when fighters stormed the upmarket Westgate mall, shooting shoppers and hurling grenades.
Government and AU troops have also come under repeated hit-and-run attacks in rural areas surrounding the settlements they have captured from al-Shabab.