More than 10,000 civilians were killed or injured in the violent attacks in the war in Afghanistan last year, the United Nations has said.

The annual report released on 15 February by the UN’s mission in Afghanistan (Unama) showed the figure had dropped by 9% in 2017, compared with the previous year.

“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,” said Unama’s chief, Tadamichi Yamamoto.

US president Donald Trump introduced a more aggressive strategy in Afghanistan last August, including a surge in airstrikes. Militants have retaliated with attacks in the capital, Kabul, in the past few weeks, killing nearly 150 people and wounding many others.

The total civilian toll last year was 3,438 killed and 7,015 wounded, according to the UN; 27% of the deaths were in attacks directed at civilians.

“When we see civilians being deliberately targeted, you wonder how long that this has to go on,” Yamamoto told a press conference in Kabul on Thursday.

Zeid Ra’ad Al Hussein, UN high commissioner for human rights, called for the “perpetrators to be held accountable”. “The people of Afghanistan, year after year, continue to live in insecurity and fear, while those responsible for ending lives and blighting lives escape punishment,” he said.

Unama reported a 5% rise in the number of women killed, at 359, with 865 injured. Child casualties stood at 3,179 (861 killed and 2,318 injured) – a 10% drop from 2016.

“We cannot sleep day and night due to the frightening sounds of firing,” an 11-year-old girl told Unama. She had been injured by a bullet during a military skirmish in Zabul province in September.

Despite the decline in overall figures, Danielle Bell, Unama’s human rights director, said: “It is the fourth consecutive year where we’ve seen more than 10,000 civilians killed or injured.

“It has indeed been a difficult year. While we did see an improvement on the battlefield by Taliban and pro-government forces, more still needs to be done.”

The International Rescue Committee’s Afghanistan director, Vicki Aken, said the numbers were “unspeakable”.

“For every child killed in this conflict, thousands more live in fear of want and need. Education in emergencies is a life-saving and life-changing intervention – helping children recover and cope with continuing adversity,” she said.

“Almost four decades of conflict has led to the education of successive generations of Afghan refugee children in particular being disrupted or forgotten. We face the threat of a lost generation in a population that has already suffered enough.

“With half the Afghan population living in Taliban-controlled or influenced areas, the prerogative for humanitarian agencies to provide assistance in contested areas is all the greater – and the IRC reaffirms its commitment to stay and deliver to those most in need, especially children.”

The deadliest attack since the UN began documenting civilian casualties in 2009 was in Kabul on 31 May last year, when a massive truck bomb killed 92 and injured 491.

Civilian casualties by pro-government international forces were partly caused by the increase in aerial bombings and attacks by Afghan and international forces, Unama said. However, the US has been the only international force carrying out airstrikes in Afghanistan.

More than 28,000 civilians have been killed and more than 52,000 wounded in Afghanistan since 2009 when UN officials started documenting the casualties.