A US airstrike in Afghanistan on Tuesday killed as many as 23 civilians, with most victims women and children, the UN says.

The strike on a compound in Helmand province was called in during a joint operation between Afghan and US forces.

Investigators said up to 10 children and eight women may have been killed. US forces say they are investigating.

Civilian casualties from aerial attacks have surged since the US announced a new Afghan strategy last year.

President Trump committed more troops to America’s longest war and significantly boosted the number of strikes targeting Taliban and Islamic State group positions in August 2017.

The rules of engagement were also loosened, allowing more bombings.