"The continued use of indiscriminate, disproportionate and illegal improvised explosive devices is particularly appalling and must immediately stop", he added in a statement.
The United Nations Assistance Mission in Afghanistan's (UNAMA) latest midyear report comes as the Pentagon deliberates on a new strategy for the United States in the country, including whether to send thousands more USA troops to break what top generals have described as a stalemate against the Taliban.
The majority of the victims were killed by anti-government forces, including the resurgent Taliban and in attacks claimed by Daesh terrorist group, the report said, underscoring spiraling insecurity in the country almost 16 years after the USA invasion.
Most of the civilian casualties occurred in a single attack in the capital Kabul on May 31, when a truck bomb killed at least 92 civilians and injured almost 500, the deadliest incident documented by UNAMA since 2001.
Deaths in the capital Kabul accounted for almost 20 percent of the toll.
Between Jan. 1 and June 30, there 1,662 civilians killed - a 2 percent increase above the previous record over the same time last year, according to the United Nations mid-year report. The truck bomb attack was the single deadliest incident documented by UNAMA since 2001.
"Many Afghan civilians are suffering psychological trauma, having lost family and friends, and are living in fear knowing the risks they face as they go about their daily lives".
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Forty per cent of the casualties were caused by bombs, mines planted by the roadside and suicide vests.
In total, anti-government forces caused the deaths of 1,141 people and injured 2,348.
The report commended Afghanistan's security forces, saying fewer civilians were caught in the crossfire compared to past year.
The figures demonstrate a 10 per cent reduction in civilian casualties from ground engagements the first six months of 2017 compared to the same period a year ago, with 434 confirmed deaths and 1,375 injuries.
Deaths in the capital Kabul accounted for almost 20 percent of the toll, according to the U.N. Assistance Mission in Afghanistan (UNAMA) report, which covers the first half of the year. After Kabul, the highest numbers of casualties occurred in Helmand, Kandahar, Nangarhar, Uruzgan, Faryab, Herat, Laghman, Kunduz and Farah provinces.
More than two-thirds of the civilian casualties were caused by anti-government forces.
Taliban spokesman Zabihullah Mujahid rejected the "biased" report, saying it did not take into account civilians killed by Afghan and coalition forces in areas controlled by the Taliban.
UN Mission said its figures only include incidents confirmed after a thorough verification process and the actual figures could be higher.