"The killing and maiming of thousands of Afghan civilians is deeply harrowing and largely preventable", Tadamichi Yamamoto, the United Nations secretary-general's special representative for Afghanistan, said in a statement.
The report said 3,498 civilians were killed and 7,920 others wounded during the conflict in Afghanistan a year ago.
The United Nations says that the number of children killed in the conflict in Afghanistan in 2016 rose by almost 25 per cent from the previous year.
Tadamichi Yamamoto, the UN Secretary-General's Special Representative for Afghanistan, said: "The killing and maiming of thousands of Afghan civilians is deeply harrowing and largely preventable".
The United Nations attributed at least 4,953 deaths and injuries to the Taliban, but in a shift in 2016, investigators documented a tenfold increase in casualties caused by Islamic State militants.
The 2016 casualties break down into 3,498 deaths and 7,920 injuries.
The disproportionate rise in child casualties across Afghanistan a year ago resulted mainly from a 66 percent increase in civilian casualties from explosive remnants of war, and most of those civilians were children, UNAMA explained.
- A truck bomb and ensuing firefight killed at least 64 people on April 19, a lot of them civilians, and wounded some 350 others a week after the start of the Taliban's "spring offensive".
The report said antigovernment elements, mainly the Taliban, were responsible for 61% of the civilian casualties past year, while government forces were to blame for 20% and pro-government armed groups and worldwide military forces, 2% each.
Of the pro-government forces, worldwide forces such as the United States accounted for 2 percent of the casualties.
He called the Afghan forces 'second major perpetrators of civilian casualties.
In November, US forces conceded that an air strike had "very likely" killed at least 30 civilians in the Kunduz area, many of them children, triggering impassioned protests in the city.
UNAMA's report Monday charted a 10-fold increase in civilian casualties blamed on Islamic State - 899, including 209 deaths.