KABUL - The number of civilians killed and wounded in the war in Afghanistan declined last year, but the number of deaths from airstrikes was on the rise, according to a new United Nations report released on Thursday.

The total number of civilian casualties decreased by 9 per cent in 2017, compared to 2016, the UN mission said in its annual report on the subject.

"The chilling statistics in this report provide credible data about the war's impact, but the figures alone cannot capture the appalling human suffering inflicted on ordinary people, especially women and children," said Tadamichi Yamamoto, the UN special representative for Afghanistan.

The 2017 Annual Report on the Protection of Civilians in Armed Conflict in Afghanistan found that between Jan. 1 and Dec. 31, 2017, there were 10,453 civilian casualties - 3,438 deaths and 7,015 wounded.

That compares to a total 11,434 casualties for the same period in 2016, when there were 3,510 deaths and 7,924 wounded.

But the decline in total deaths was tempered by the report's finding that the number of airstrikes conducted by international military forces and Afghan air forces increased significantly - and with it the number of airstrike-related deaths.

The United Nations Assistance Mission in Afghanistan documented 631 civilian casualties - 295 deaths and 336 wounded - from aerial operations conducted by pro-government forces. That's a 7 per cent increase from 2016, and the highest number from airstrikes in a single year since 2009. Aerial operations accounted for 6 per cent of all civilian casualties in Afghanistan in 2017.

Danielle Bell, a UN official for human rights in Afghanistan, said the reduction "is an important step" but cautioned that 2017 was the "fourth consecutive year, where the emission recorded more than 10,000 civilian causalities."

Afghanistan has been mired in conflict since 2001 when the United States invaded after 9-11. The U.S. and NATO forces formally concluded their combat mission at the end of 2014 and shifted to a training role, but a resurgent Taliban stepped up their attacks and an affiliate of the Islamic State group has also emerged. Between Jan. 1, 2009, and Dec. 31, 2017, the conflict in Afghanistan has claimed the lives of 28,291 civilians and wounded 52,366 others, according to the report.

Suicide and complex attacks - when assailants combine two or more modes of attack on one target at the same time - caused 22 per cent of all civilian casualties in Afghanistan in 2017, with 16 per cent of all civilian casualties occurring from such attacks in the capital of Kabul.

The report attributes close to two thirds of all casualties to militant groups fighting the government, mainly the Taliban, but also IS and other, undetermined anti-government elements.

Less than 5 per cent of the civilian casualties were caused by Afghan government forces and their allies, the international troops, while 11 per cent of the casualties were caused by unattributed cross-fire during fighting between Afghan forces and anti-government elements, the report said.

Yamamoto, who also heads UNAMA, expressed deep concern at the increased harm to civilians caused by suicide attacks.

"I am particularly appalled by the continued indiscriminate and unlawful use of (improvised explosive devices) such as suicide bombs and pressure-plate devices in civilian populated areas," he said. "This is shameful."

UNAMA also documented an increase in attacks against places of worship, religious leaders and worshippers, recording 499 civilian casualties with 202 deaths and 297 injured, during 38 such attacks in 2017. This amounted to three times as many attacks as in 2016, double the number of deaths and 30 per cent more total civilian casualties.

In 2017, women continued to suffer at levels comparable to 2016. Contrary to the overall decrease in civilian casualties, women casualties increased by less than one per cent, and women deaths increased by 5 per cent. Ground engagements remained the leading cause of harm to women, though UNAMA documented a decrease of 11 per cent in women casualties from ground fighting. The next leading cause, suicide bombings and complex attacks, caused more than double the number of women casualties in 2017 than in 2016.

In line with the overall reduction in civilian casualties in 2017, child casualties decreased by 10 per cent, compared to 2016. UNAMA documented 3,179 child casualties in 2017, of which 861 were deaths and 2,318 were wounded.

"When we document these appalling civilian causality figures, it hurts, because it counters the best interest of this country," Yamamoto told reporters in Kabul on Thursday.

"Each of these figures represents a hope crushed for a better future," he added.