A Nato air strike has killed 14 people, all civilians, in south-west Afghanistan's Helmand province, local officials say.

The strike took place in Nawzad district after a US Marines base came under attack on Saturday, BBC reports.

The air strike, which was targeted at insurgents, instead struck two civilian homes, killing two women and 12 children, reports say.

Nato and Afghan troops are looking into the incident.

Earlier, a coalition soldier was killed in a gun battle with insurgents in the area and an air strike was called in, said a spokesman for the international mission.

President Hamid Karzai has criticised Nato for not doing enough to prevent such deaths, especially during "night raids" and has called on the country's ministry of defence to stop what he described as "arbitrary" operations by foreign forces.