The United Nations says the number of civilians killed in Afghanistan during the first four months of this year as a result of the war has dropped by 21 percent compared to the same period in 2011.

Jan Kubis, the UN special representative for Afghanistan, also said that about eight out of 10 civilian deaths in Afghanistan were caused by Taliban militants or their antigovernment allies.

He says fewer than one out of 10 civilian deaths were caused by Afghan government forces or the NATO-led International Security Assistance Force (ISAF).

The rest were unattributed.

Civilian deaths from NATO air strikes have drawn criticism from Afghan President Hamid Karzai, who says they turn ordinary Afghans against his Western-backed government.