The report apparently refers to civilians killed during Afghan and U.S. military operations against insurgents, such as airstrikes and night raids on militant hideouts. Insurgents often hide among civilians.
The U.S. formally ended its combat mission in Afghanistan in 2014 but still provides extensive air and other support to Afghan forces battling militants. The U.N. report said 403 civilians were killed by Afghan forces in the first six months of the year and another 314 by international forces, a total of 717. That's compared to 531 killed by the Taliban, an Islamic State affiliate and other militants during the same period.
It said 300 of those killed by militants were directly targeted. The Taliban have been carrying out near-daily attacks, mainly targeting security forces. There was no immediate comment from the Kabul government or the Afghan military on the report.
A NATO official stressed that the alliance is now in a non-combat mission in Afghanistan that trains, advises and assists the country's security forces. The alliance is "not complacent" and shares U.N. concerns over Afghan civilian casualties, the official said, adding that the "best way to end the suffering of civilians is to focus on the political settlement of the conflict and to continue all efforts to reduce violence."
"We thoroughly investigate every allegation of civilian casualties, and we train the Afghan security forces to ensure that they take utmost caution in order not to harm civilians," said the official, speaking on condition of anonymity in line with regulations.
The Taliban have rejected calls for a cease-fire as they hold talks with the U.S. aimed at ending the 18-year war. An Islamic State affiliate has meanwhile launched attacks targeting security forces as well as minority Shiites.
"Parties to the conflict may give differing explanations for recent trends, each designed to justify their own military tactics," said Richard Bennett, the human rights chief of the U.N. Assistance Mission in Afghanistan, which released the report.
The situation for ordinary Afghans would be improved, he said, "not just by abiding by international humanitarian law but also by reducing the intensity of the fighting." The report said one in three casualties was caused by ground combat and a fifth were caused by roadside bombs. Aerial operations accounted for around 14% of the casualties.
The Taliban issued a statement saying the part of the U.N. report blaming them for 38% of Afghan civilian casualties was not true. "Many people counted as civilians in this report were targeted by the Taliban because of their links to the intelligence service or because they cooperated with military operations," the Taliban said.
Earlier in the day, the Taliban praised the killing of two U.S. service members Monday in southern Kandahar province. The Afghan soldier who turned his gun on the Americans was wounded and is in custody, according to U.S. officials.
The Taliban called the shooter a "hero" and said the Afghan soldier had opened fire at the Americans inside a military base in the Shah Wali Kot district in Kandahar. The U.S. military has so far not identified the slain Americans, pending notification of their families.
Even with the Taliban-U.S. talks underway, there appears to be no end in sight for the violence. A suicide bomber on a motorcycle detonated his explosives at a market in southern Kandahar province on Tuesday morning, killing at least three children, said Jamal Naser Barekzai, spokesman for the provincial police chief.
A Taliban attack on a checkpoint left three police officers dead in northern Baghlan province, said Jawed Basharat, spokesman for the provincial police chief. Late on Monday, insurgents targeted a checkpoint in the Kushk Kuhna district in western Herat province, killing at least 11 Afghan security forces, said Wakil Ahmad Karokhi, a provincial councilman.
There was no immediate claim of responsibility for the latest attacks.
Associated Press writers Amir Shah in Kabul, Afghanistan, and Maamoun Youssef in Cairo contributed to this report.