1218 GMT February 18, 2020
The bloody milestone comes as the US steps up its air campaign in Afghanistan while pushing for a peace deal with the Taliban, who now control or influence more parts of the country than at any time since they were ousted in 2001, AFP reported.
During the first three months of 2019, international and pro-government forces were responsible for the deaths of 305 civilians, whereas militant groups killed 227 people, the United Nations Assistance Mission in Afghanistan (UNAMA) said in a quarterly report.
The majority of the deaths resulted from US airstrikes or from search operations on the ground, primarily conducted by US-backed Afghan forces, some of which UNAMA said "appear to act with impunity".
"UNAMA urges both the Afghan national security forces and international military forces to conduct investigations into allegations of civilian casualties, to publish the results of their findings, and to provide compensation to victims as appropriate," the report states.
UNAMA started compiling civilian casualty data in 2009 amid deteriorating security conditions in Afghanistan.
It is the first tally since records began that shows pro-government forces have killed more civilians than militants have, though insurgents were responsible for more than twice as many injuries as were pro-government forces.
Colonel Dave Butler, the spokesman for US Forces-Afghanistan, said the US military holds itself "to the highest standards of accuracy and accountability" and that it strives for precision in all its operations.
According to US Air Force Central Command, the US dropped 7,362 bombs in Afghanistan in 2018, the highest number since at least 2010, and up from 4,361 in 2017.
While other nations may contribute logistical or technical support, it is US aircraft that conduct most strikes. Afghanistan's fledgling air force is also flying more sorties.
The US has sent huge B-52 bombers on runs over the country and benefited from an increase in aerial hardware as operations against the Daesh terror group in Iraq and Syria tapered off.
UNAMA's report did, however, also find that civilian casualties dropped 23 percent compared with the first three months of 2018.
In all, UNAMA documented 1,773 casualties in the last quarter: 581 deaths and 1,192 injured – the lowest first-quarter toll since 2013.
The drop was driven by a decrease in the use of suicide bomb attacks, but UNAMA did not know if this trend came as a result of a harsh winter or if the Taliban were trying to kill fewer civilians during peace talks.
In contrast, the first three months of 2018 saw a spike in horrific attacks that skewed numbers higher for that part of the year compared to 2019. For instance, more than 100 people were killed in Kabul in January 2018 when an explosives-packed ambulance blew up.
UNAMA chief Tadamichi Yamamoto, who also serves as the UN secretary general's special representative for Afghanistan, said a "shocking number" of civilians are still being killed or maimed.
"All parties must do more to safeguard civilians," Yamamoto said in a statement.
"Anti-government elements need to stop deliberately targeting civilians ... pro-government forces are called upon to take immediate measures to mitigate the rising death toll and suffering caused by air strikes and search operations," he added.
Last year was the deadliest yet for Afghan civilians, with 3,804 killed, according to UNAMA.