Kabul --

Violence in Afghanistan is up nearly 40 percent over last year, a U.N. report released Wednesday found, contradicting claims by the U.S.-led coalition that security has improved since last year.

The U.N. report, information for which is compiled by the U.N. mission in Kabul and submitted to the Security Council quarterly, said that as of the end of August, there had been an average of 2,108 "security incidents" each month this year, a 39 percent increase compared with the comparable period in 2010.

The average number of suicide attacks monthly, 12, remained unchanged, the report said, but more of those attacks were complex and coordinated, involving more than a lone bomber, the report said. The monthly average of three such complex attacks this year is 50 percent higher than the number for the like period in 2010.

A report from the U.S.-led International Security Assistance Force in August painted a sharply different picture.

"Throughout 2011 ISAF has seen significant security improvements throughout Afghanistan and violence is down in 12 of the past 16 weeks as compared to the same period in 2010," the coalition's report said.

The U.N. report found that violence remained high in Afghanistan's south and southeast, areas where U.S. troops have stepped up operations against Taliban forces.

It also found that civilian casualties have risen steadily: up 5 percent in June, July and August from the same months last year. That followed a 15 percent increase that the United Nations reported for the first six months of the year.

All told, 971 Afghans died in violence from June through August, the U.N. report said. The actions of the Taliban and its allies caused 77 percent of those deaths, the report found. The United States and its allies caused 12 percent of those deaths.

Forty-five percent of civilian casualties were the result of suicide bombs and improvised explosive devices, the report said. The greatest coalition cause of death remained NATO air strikes.