KABUL, Afghanistan (AP) -- The number of civilians killed in the Afghan war jumped 25 percent in the first half of 2010 compared with the same period last year, with insurgents responsible for the spike, the United Nations said in a report Tuesday.

Soldiers with the NATO- led International Security Assistance Force (ISAF) arrive at the scene of a militant attack in Kabul, Afghanistan on Tuesday, Aug. 10, 2010. Two suicide attackers struck a building rented by a private security company in Afghanistan's capital Tuesday, detonating their explosive vests to kill two company drivers, police said. (AP Photo/Musadeq Sadeq) Shortly after the U.N. released its report in Kabul, two gunmen with explosives strapped to them tried to storm the office of an international security company in the capital. When guards fought back, the men detonated their explosives, killing two Afghan drivers.

The U.N. report showed a reduction in civilian casualties from NATO action, but the overall rise in deaths indicated that the war is getting ever-more violent - undermining the coalition's aim of improving security in the face of a virulent Taliban insurgency.

"The human cost of this conflict is unfortunately rising," said Staffan De Mistura, the top U.N. envoy in Afghanistan. "We are very concerned about the future because the human cost is being paid too heavily by civilians. This report is a wake-up call."

According to the U.N. report, 1,271 Afghans died and 1,997 were injured - mostly from bombings - in the first six months of the year. There were 1,013 civilian deaths in the first six months of 2009.

The U.N. said insurgents were responsible for 72 percent of the deaths - up from 58 percent last year.

In much of the south, people say they are too scared to work with NATO forces or the Afghan government because they will then be targeted by insurgents. And the risk of attack makes travel, running a business or any sort of community organizing or political campaigning dangerous.

The attack on Hart Security in Kabul started with a gunbattle as the assailants tried to shoot their way in to the compound in the largely residential Taimani neighborhood about 3:30 p.m. (1100 GMT, 7 a.m. EDT), said Abdul Ghafar Sayedzada, chief of criminal investigations for the Kabul police.

After the assault, a group of men could be seen carrying a body out of the building toward a waiting police truck. One of the men carrying the body was weeping, according to an Associated Press reporter at the scene.

The attack appeared timed to coincide with the end of the company's workday, Sayedzada said.

Area residents said they heard shooting about the same time as the blast.

"I was about to park my car when I heard gunfire. I turned and saw shooting between the security guards and two other people. They were trying to get in the building," said Mohammad Sharif, who lives nearby. "In the middle of that fighting suddenly there was a big explosion."

One of the security guards was also wounded, Sayedzada said.

The Kabul deaths were not the day's only civilian casualties. Three civilians were killed when their car struck a roadside bomb just outside the eastern city of Ghazni, according to deputy provincial governor Kazim Allayar. And an insurgent-planted bomb killed an Afghan civilian near southern Kandahar city on Monday, according to NATO forces.

De Mistura said militants were using larger and more sophisticated explosive devices throughout the nation.

"If they want to be part of a future Afghanistan, they cannot do so over the bodies of so many civilians," de Mistura said.

De Mistura said that does not dissuade the U.N. from seeking a negotiated peace between the government and the Taliban, but he called on insurgent groups to consider whether they are not hurting their own long-term goals.

"One day, when unavoidably there will be a discussion about the future of the country, will you want to come to that table with thousands of Afghans, civilians, killed along the road?"

Deaths from U.S., NATO and other pro-government forces dropped in the first six months of 2010. The report said that 223, or 18 percent, of the Afghan deaths were due to U.S., NATO and other pro-government forces. That was down from 310 deaths, or 31 percent, during the first six months of last year, primarily because of a decrease in airstrikes, the report said.

Even so, air attacks were the largest single cause of civilian deaths caused by pro-government forces - accounting for 31 percent.

Gen. Stanley McChrystal, the former NATO commander, introduced strict rules on air strikes and called on soldiers to assess the likelihood of civilian casualties before taking any action. His successor, Gen. David Petraeus, has continued the policy.

"Every Afghan death diminishes our cause," Petraeus said in a statement. He also noted that even the increase in insurgent-caused deaths can hurt NATO's effort.

"We know the measure by which our mission will be judged is protecting the population from harm by either side. We will redouble our efforts to prevent insurgents from harming their neighbors," Petraeus said.

Though bombs continued to be the largest killer, there was a large jump in deaths from assassinations, particularly in the last few months.

There were about four assassinations or executions of civilians a week in the first six months of 2009. That jumped to about seven per week in the first six months of this year, spiking in May and June to 18 per week.

"These figures show that the Taliban are resorting to desperate measures, increasingly executing and assassinating civilians, including teachers, doctors, civil servants and tribal elders," said Rachel Reid, Afghanistan researcher for Human Rights Watch. "Targeting civilians violates the laws of war."

The Taliban has called on its fighters to avoid civilian casualties, but the group pointedly excludes anyone allied with the government from this protection. So mayors, community elders taking foreign money for development projects and mullahs seen as supporting the government have all become targets.

Children have also increasingly become casualties of the war. The report says 176 children were killed and 389 others were wounded - up 55 percent over the same six-month period last year.

Elsewhere in Afghanistan, seven Afghan policemen were killed Monday in attacks in southern Helmand province, police officials said.

In Laghman province in the east, seven Afghan soldiers have died and 14 have been wounded in ongoing fighting with insurgents on the outskirts of the provincial capital of Mehtar, said Gen. Mohammad Zahir Azimi, a spokesman for the Defense Ministry. He confirmed reports that up to 20 Afghan soldiers have gone missing in the province and are in the hands of the Taliban.