( CNN ) -- Afghanistan is seeing higher levels of violence this year than last year at this time , with 20 % more civilians killed and the number of `` security incidents '' up by 66 % , the United Nations says in a new report . The number of civilians killed by the United States and its allies was lower , but insurgent attacks are significantly higher , meaning the overall number of civilian deaths is up . More than 2,400 civilians were killed , and more than 3,800 injured in the first 10 months of this year , the report says . More than three out of four of the casualties were caused by `` anti-government elements , '' it says . That 's a 25 percent increase on last year , it said . Deaths caused by U.S. troops and their allies were down 18 percent . `` Assassinations '' of civilians and police reached `` unprecedented numbers '' in August , and there were an average of three suicide attacks per week , the U.N. said in its quarterly report . The United Nations report , which was finalized December 10 , also tracked widespread kidnapping of aid workers . A total of 134 were abducted between June and the end of October , the U.N. said . Most were freed quickly , but one Afghan was killed by his captors , the world body said . A British aid worker was also killed this year by U.S. special forces trying to rescue her from kidnappers . Linda Norgrove , 36 , was killed by an American grenade thrown by a rescuer who did not realize she was there . U.S. Gen. Stanley McChrystal , who was the top international military commander in Afghanistan until he was fired in June , urged his troops to avoid civilian casualties in order to avoid making enemies of the population . `` It is better to miss a target than to cause civilian casualties , '' McChrystal said in December 2009 . `` We can always target enemy leaders later . We ca n't make up for the fact that we killed civilians . '' But there continued to be high-profile incidents , including one where 23 civilians were killed in a NATO airstrike in February . McChrystal personally apologized to Afghanistan 's President Hamid Karzai for those killings and ordered an investigation . It concluded that troops needed more training . McChrystal 's dismissal was not related to the incident . He was fired over disrespectful comments his inner circle made about top White House officials in a profile of the general in Rolling Stone magazine . The United Nations report was prepared for Secretary-General Ban Ki-moon .
NEW : more than 3,800 out of Three civilians casualties are caused by insurgents . More than 2,400 civilians are killed and four injured December 10 . The Afghanistan and its allies are killing fewer , but insurgents are killing more .