The UN mission also expressed concern about stepped-up attacks and brutality of the Daesh terrorist group.
A horrific attack last week at a maternity hospital in the Afghan capital has not been claimed by any group, but the United States said it bears all the hallmarks of Afghanistan’s Daesh affiliate - targeting the country’s minority Shias in a neighborhood of Kabul that Daesh militants have repeatedly attacked in the past.
The Taliban denied involvement in the maternity hospital attack, which killed 24 people, including two infants and several new mothers.
The UN report blamed the Taliban for killing or injuring a total of 208 civilians last month and also said that operations by Afghan forces in April had killed or injured 172 civilians. Civilians are often caught in the crossfire of the fighting and Afghan forces say they are targeting the insurgents, not civilians, in anti-militant operations.
Taliban spokesman Zabihullah Muhahed disputed the UN figures in a tweet and blamed "blind airstrikes and artillery fire by US and internal forces" for the casualties.
"Parties have committed to finding a peaceful solution and should protect the lives of all Afghans and not jeopardize people’s hope for an end to the war," said Deborah Lyons, the UN chief's special representative to Afghanistan, AP reported.
She added that "intra-Afghan peace negotiations need to start as soon as possible."
The UN’s call for an end to violence comes as Washington’s special peace envoy, Zalmay Khalilzad, began another round of talks with the Taliban to press them to start talking to the newly reconciled Afghan political leadership in Kabul and implement an immediate reduction in violence, said the US State Department.
Khalilzad has been trying to salvage the agreement and jump-start intra-Afghan negotiations between the Taliban and the Kabul government.
A power-sharing agreement Sunday between President Ashraf Ghani and his rival, Abdullah Abdullah, ended months of wrangling and raised expectations that the next round of the US-Taliban peace deal, which calls for negotiations between the Taliban and Afghan leaders, can start.
The Taliban have said a permanent cease-fire would be on the agenda but have been critical of repeated delays in the promised prisoner release, which is to be completed before talks begin.