Militants have stepped up their suicide attacks on civilians, the UNAMA said in its June report to U.N. Secretary General Ban Ki-moon.
The biggest killer of civilians in Afghanistan is roadside bombs, followed by suicide bombs, which frequently kill civilians when the insurgents are unable to reach their intended targets, The New York Times reported.
"Despite the Taliban's public statements that the offensive should target exclusively military objectives and ensure the protection of civilians, indiscriminate attacks against civilians continued," the U.N. report said.
Just 10 percent of civilian casualties were attributed to the government and its coalition allies.
Insurgent attacks in recent days have resulted in dozens of deaths. Thursday, a pair of mines planted on a road in Herat Province exploded, killing 23 civilians and wounding eight, Afghan officials said.
Also Thursday, a suicide bomber in a car loaded with explosives killed two Afghan security force members and nine civilians.
Officials said the driver attempted to break through the gates of Forward Operating Base Gardez, in eastern Paktia Province, but the car exploded before he got inside the base.
The Taliban claimed to have killed 17 foreign soldiers at the forward operating base in Herat Province, but a spokesperson for the NATO-led International Security Assistance Task Force said there were no reports of coalition casualties there.