Girls killed in Afghan roadside blast

At least four girls have been killed by a roadside blast in the southern Afghan province of Helmand, officials say.

The girls, said to be aged between seven and 12, were attending a wedding and had gone to collect water from a stream when the explosives detonated.

Afghan forces have taken over security responsibility, and improvised explosive devices (IEDs) are one of their biggest challenges.

Helmand is one of Afghanistan's most volatile provinces.