KABUL, Afghanistan -- Afghan civilian deaths dropped 22 per cent in the first six months of 2012 compared with a year ago, but the number of civilians killed in targeted assassinations surged, the United Nations said in a report released Wednesday.

The overall reduction was largely due to a decrease in the number killed by insurgents' homemade bombs and suicide attacks, the report said. The number of civilians who died in NATO attacks including airstrikes also fell.

It was the first time the UN data had shown such a sustained reduction in civilian deaths since it started counting in 2007. Even so, UN officials cautioned that fighting started to pick up in May and that civilian casualties are already spiking again.

"This report does not suggest that Afghans are necessarily safer or better protected in their communities, nor does it suggest any real or concerted attempt by anti-government elements to minimize civilian casualties," Nicholas Haysom, the deputy UN chief in Afghanistan, told reporters in Kabul. In fact, the UN said when it previously reported a drop in civilian casualties for the first four months of the year that much of that decrease could be attributed to the particularly harsh winter.

In all, 1,145 civilians were killed in Afghanistan between January and June of this year, according to the report. That's down from 1,462 in the first half of 2011. Injuries to civilians caught up in the crossfire also dropped.

James Rodehaver, the head of human rights for the UN mission in Afghanistan, called the six-month reduction in civilian casualties "a very hollow trend." He explained that the gap between last year and this year had already started to close in May and June as warm weather brought the start of the traditional fighting season.

He said preliminary figures for July, which was not covered by the report, show a 5 per cent increase in civilian casualties -- including injuries -- over 2011.

The United Nations previously reported that civilian deaths had dropped 36 per cent in the first four months of 2012 compared with 2011. The 22 per cent drop reported Wednesday shows that the positive winter trend has already been eroded by the spring and summer violence.

The rise in targeted killings has been particularly sharp, the UN said. The Taliban regularly target anyone from government officials to local elders who agree to work with the government or the international military for assassination. The insurgents have said that anyone who associates with the government is a collaborator and therefore not a civilian.

Civilian deaths from targeted killings and assassinations jumped 34 per cent from 255 in this year's period from 190 in 2011, the UN said.

The UN stressed that bombings and indiscriminate attacks continue, along with targeting of places frequented by women and children. In one particularly disturbing trend, insurgent attacks against schools increased compared with a year ago. And Haysom noted that in July there were five separate insurgent attacks against mosques or imams.

Rodehaver did note, however, that civilian casualties did decrease in May and June, if by a smaller amount than the winter months. It was unclear if the overall drop was also affected by pressure from international and Afghan forces or a strategy change on the part of the insurgency.

By their nature, targeted killings tend to result in fewer deaths per incident. Data from NATO forces in the country suggests that attacks are up significantly in May and June compared with last year, even if the deaths were slightly down.

"Some factors reflect improvements in the security environment while others indicate that anti-government elements may be refocusing their efforts or holding ground in some areas," the report said.

Homemade bombs killed 327 civilians between January and June, down from 444 in the first six months of 2011. Insurgents also killed fewer civilians in suicide bombings that in the year before. While civilian deaths caused by NATO and Afghan forces have been decreasing for years, this is the first time the UN data -- the most widely used on the subject -- showed a decrease in insurgent-caused casualties.

But even with the reduction, the Taliban and other militants are responsible for the overwhelming majority of civilian deaths in the country. About 77 per cent of the deaths between January and June can be attributed to insurgents, according to the report.

And insurgent-placed homemade bombs continued to be the deadliest weapon for civilians, accounting for 29 per cent of all such deaths in the period.

In the latest such incident on Tuesday, a remote-controlled roadside bomb struck a bus traveling northwest of Kabul, killing at least nine passengers.

Civilian casualties attributed to the international military and the Afghan government declined as both groups strengthened policies to protect civilians, the UN said. There were 165 civilians killed by international, Afghan or allied forces in the first half of the year, down 35 per cent from 255 in 2011. The majority of these deaths -- 127 -- came from airstrikes, though that was also a reduction from the previous year.