KABUL, Afghanistan  With an average of an assassination a day and a suicide bombing every second or third day, insurgents have greatly increased the level of violence in Afghanistan, and have become by far the biggest killers of civilians here, the United Nations said in a report released publicly on Saturday.

The report also confirms statistics from the NATO coalition, which claimed a continuing decrease in civilian deaths caused by the United States military and its allies. At the same time it blames stepped-up military operations for an overall increase in the violence.

Especially alarming were increases in suicide bombings and assassinations of government officials in a three-month period ending June 16, and a near-doubling of roadside bombings for the first four months of 2010 compared with the same period in 2009.

“The number of security incidents increased significantly, compared to previous years and contrary to seasonal trends,” the report said, adding that most of this was a consequence of military operations in the southern part of the country, particularly Helmand and Kandahar Provinces, where increased NATO military operations have been under way since February.