The bomb exploded at a checkpoint in the small central town of Beledweyne, some 325 kilometres (200 miles) north of the capital Mogadishu, where last month Al-Qaeda-linked Shebab insurgents claimed responsibility for a bomb attack which ripped a hole in a passenger plane shortly after takeoff.
"A laptop computer went off at the screening area, and the security forces have also managed to defuse two other explosive devices, one of them planted in a printer," Police Lieutenant Colonel Ali Dhuh Abdi told reporters. "Six people were wounded, two of them policemen."
There was no immediate claim of responsibility for the attack.