At least three Somali soldiers on a ordnance-clearing mission were killed on Monday by a roadside bomb just 90 km (60 miles) north of the capital, from where Islamists militants were routed six years ago.

Al Qaeda-linked al Shabaab claimed responsibility for the attack at a checkpoint on the outskirts of the town of Shalanbood in the Lower Shabelle region.

"We went out of town in search of bombs but one had been planted right on the spot where we were based," regional military official, Mohamed Nur, said.

"The blast killed three of my colleagues and injured four others," he told Reuters.

The insurgents gave a higher toll.

"We are behind the bomb at the checkpoint that killed four soldiers, including two officials," al Shabaab's military operations spokesman, Sheikh Abdiasis Abu Musab, said.

The group carries out frequent attacks in and around the capital Mogadishu in its decade-old attempt to topple the Western-backed government and drive out African Union peacekeeping troops.

Somalia has been at war since 1991, when clan-based warlords overthrew dictator Siad Barre and then turned on each other.

(Reporting by Feisal Omar and Abdi Sheikh; Writing by Aaron Maasho; Editing by Louise Ireland)