Between January and March, 161 children were killed and 449 others injured -- a 29 percent increase from a year earlier -- the UN's mission in Afghanistan said in a report.
Danielle Bell, the mission's human rights director, said women and children have suffered the most as the insurgents have launched more bomb attacks in populated areas.
"In the first quarter of 2016, almost one third of civilian casualties were children," said Bell in the report.
"Increased fighting in populated areas continues to kill and injure women and children at higher rates that the general population."
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The figures come days after the Taliban launched its spring offensive by trying to retake control of Kunduz, the northeastern provincial capital they briefly captured last year.
The militants have intensified their insurgency since the end of NATO's combat mission in 2014, launching brazen attacks on urban areas that saw last year become the bloodiest for civilians on record.
The Taliban were responsible for six out of every 10 casualties, according to the UN's report.
Last year, there were 11,002 civilian casualties, including 3,545 deaths, according to UN figures released in February.