Updated

A Somali police officer says a roadside bomb has killed six people and injured three others.

Col. Ahmed Nur says the bomb struck a minibus carrying farmers near Bal'ad town just north of the capital, Mogadishu, on Sunday.

There is no immediate claim of responsibility for the bombing in an area that has seen clashes between government forces and fighters with the al-Qaida-linked al-Shabab extremist group.

Al-Shabab carries out guerrilla attacks across large parts of southern and central Somalia.

The roadside bombing comes little over a week after a massive truck bombing in Mogadishu killed at least 358 people in the country's worst attack.

Somalia's president has told troops to prepare for a "state of war" and new offensive against al-Shabab.