Jan Kubis, the U.N. special representative to Afghanistan, said 579 civilian deaths and 1,216 civilian injuries were recorded from January through April, The New York Times reported.
The United Nations said 9 percent of the casualties were attributed to pro-government forces, which include international troops and Afghan security forces. Seventy-nine percent of the casualties were attributed to anti-government forces, including the Taliban, and 12 percent were unattributed.
Last year, international troops and Afghan forces were responsible for 14 percent of the casualties, while the percentage caused by the Taliban was virtually unchanged, the Times said.
"Regrettably, unfortunately the anti-government forces, they don't show any improvement in protection for civilians," Kubis said during a news conference in Kabul, Afghanistan's capital. "They issue statements about protecting civilians, but in practice they use such indiscriminate destructive weapons."
The data released Wednesday indicate the first quarter was the first time a reduction in civilian casualties was recorded since the United Nations began tracking such statistics in 2007, the Times said. Human rights officials expressed caution about the sustainability of reduced casualties since the past winter was harsh compared with the relatively mild winter a year earlier.
"The downturn in the number of armed clashes and the impact of the harsh weather is much more likely to have impact on Taliban operations than on government or ISAF [International Security Assistance Force] operations," said James Rodehaver, acting head of the United Nations' human rights office in Kabul.