NATO says a roadside bombing in southern Afghanistan has killed four civilians and critically injured a fifth.

The coalition says the attack happened Friday in Trinkot City in Uruzgan province.

No one has claimed responsibility for the blast, but roadside bombs are frequently planted by Taliban-led insurgents fighting a decade-long war against foreign and Afghan forces.

Friday's attack comes a day after a roadside bomb killed 10 Afghan police officers in Helmand province. The Taliban said it was behind Thursday's bombing in the Nad Ali district.