Story highlights The Taliban criticize the U.N. report, saying it's "in favor of Americans"

The increase in deaths and injuries in the first half of this year reverses a drop in 2012

Last year's decline was the first recorded since the U.N. started publishing the data

The U.N. says improvised explosive devices are the main factor behind the rise

Civilian casualties in Afghanistan increased 23% in the first six months of this year, the United Nations said in a report released Wednesday.

The rise in the number of ordinary Afghans killed and injured reverses a decline in 2012 . That was the first drop in civilian casualties since the U.N. began publishing the figures in 2007.

The increase in deaths and injuries so far this year was mainly driven by the stepped up use of improvised explosive devices (IEDs), the United Nations Assistance Mission in Afghanistan said in its report.

Civilian deaths increased 14% from the first six months of 2012 to 1,319, the report said, while injuries rose 28% to 2,533.

"The violent impact of the conflict on Afghan civilians marked by the return of rising civilian casualties in 2013 demands even greater commitment and further efforts by parties to the conflict to better protect civilians who are increasingly being killed and injured in the cross-fire," said Jan Kubis, the U.N. secretary-general's special representative for Afghanistan.

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Nearly three-quarters of all civilian casualties in the first half of the year resulted from actions by anti-government groups, notably the Taliban, the U.N. report found.

The remainder were caused by pro-government forces (9%), ground engagements between pro- and anti-government forces (12%) and unattributed factors like unexploded ordnance (5%).

The report singled out the devastating effect of the use of IEDs, which caused 35% of deaths and injuries. The devices killed 443 civilians and injured 917. That's a 34% increase in overall casualties from the first half of 2012.

"The increase in the indiscriminate use of IEDs and the deliberate targeting of civilians by anti-government elements is particularly alarming and must stop," Kubis said.

The NATO-led International Security Assistance Force in Afghanistan welcomed the report, saying it had taken "a number of positive steps to reduce the number of civilian casualties in this country."

"Unfortunately, the Taliban's demonstrated lack of regard for human life has resulted in nearly 90 percent of all civilian casualties so far this year. By continuing the indiscriminate use of improvised explosive device attacks despite the huge toll on Afghan men, women and children, the Taliban proves it does not take their pledge to protect innocent civilians seriously," ISAF said.

But the Taliban criticized the report, saying it was "in favor of Americans and part of the propaganda against the Taliban."