Officials in eastern Afghanistan say NATO troops have killed six people during an operation, while the United Nations released a report saying the number of civilians killed during the war this year is higher than at this time in 2010.

Residents demonstrated Thursday in the city of Khost, where local officials said the six civilians were killed. NATO said it carried out an operation against Haqqani militants in the area and had no reports of civilian casualties.

Meanwhile, the U.N. mission in Afghanistan said Thursday more than 1,400 civilians were killed in the first six months of this year, and attributed the deaths to increased ground fighting, roadside bombs, suicide attacks and a rise in NATO air strikes.

The report blamed insurgents for 80 percent of civilian deaths, and said foreign and government forces were responsible for 14 percent of the killings.

The United Nations said that while the overall number of civilian deaths linked to the U.S.-led NATO coalition fell by 9 percent, there was an increase in the number of those killed by air strikes.

Violence in Afghanistan has hit the worst levels since the U.S.-led invasion in 2001, and May was the deadliest month for Afghan civilians since the United Nations mission began compiling statistics four years ago.