Five others were seriously injured when their vehicle ran over an improvised explosive device in the Gedo region, near the Kenya-Somalia border.

The names of the killed soldiers have not been revealed, but a former Kenyan presidential aspirant said on Twitter that his younger brother was among the dead.

The attack has been blamed on al-Qaeda-linked al-Shabab group, which has carried out similar strikes against civilians and security convoys.

The killed soldiers were part of the African Union Mission in Somalia - a force deployed to the country to help the federal government fight the militants.

Recent months have seen a surge in attacks that have targeted public areas, government installations and security check points.

It comes as the country grapples with a much-delayed parliamentary election, with analysts saying the rise in attacks is meant to scuttle the process that will culminate in the elected MPs selecting a new president.