The U.S. military on Wednesday once again condemned the actions of some of its troops in Afghanistan after photographs surfaced of smiling soldiers posing with dead insurgents in the latest battlefield scandal.

The photographs, obtained by the Los Angeles Times, show soldiers posing next to Afghan corpses, including the mangled body of a suicide bomber hoisted by his ankles. In another shot, which the newspaper described but did not publish, two soldiers hold up a dead man’s hand, extending his middle finger.

The 18 photographs were taken in 2010 in Zabul province by soldiers from the 82nd Airborne’s 4th Brigade Combat Team, the newspaper reported. Although the pictures were two years old, the fresh disclosure of misconduct extends a string of recent incidents in which U.S. troops have disrespected the dead, allegedly killed Afghan civilians and desecrated the Koran.

U.S. officials, concerned that the cumulative effect will be the further alienation of an Afghan public weary of foreign military occupation, disavowed the actions depicted in the photographs and said they had started investigations.

In Brussels, where NATO ministers were meeting to discuss the war’s progress, Defense Secretary Leon E. Panetta apologized. He said he “strongly condemned” the soldiers’ actions but portrayed them as immature reactions to battlefield stress.

“This is war, and I know war is ugly and is violent,” Panetta said. “I know young people sometimes caught up in the moment make some very foolish decisions.”

“I am not excusing that behavior,” he added.

Rep. Adam Smith (Wash.), the top Democrat on the House Armed Services Committee, said the problems underscored the need to transfer responsibility for security to Afghan forces as quickly as possible.

“Our presence by its very nature creates tension between us and the local population,” Smith said in an interview Wednesday. “Past a certain point, a foreign presence is as destabilizing as it is stabilizing, and that’s what these incidents are pointing out.”

A series of setbacks

The photographs mark the latest public relations setback for the U.S. military as it seeks to gradually withdraw from Afghanistan.

In January, an Internet video showed Marines laughing as they urinated on the corpses of three insurgent fighters. In February, riots erupted after U.S. service members incinerated copies of the Koran in what NATO officials deemed an accident. In March, an Army staff sergeant was charged with killing 17 Afghan villagers, mostly women and children, in Kandahar province.

Meanwhile, distrust is building between U.S. forces and their Afghan allies. The number of treacherous, lethal attacks by uniformed Afghan soldiers and police officers against NATO troops and trainers has risen substantially this year.

In addition to condemning the actions depicted in the latest batch of battlefield photographs, the Pentagon also criticized the Los Angeles Times for publishing them.

Panetta said defense officials had urged the Times to suppress the pictures. George Little, the Pentagon press secretary, suggested that the newspaper’s decision could put U.S. troops at risk. “The danger is that this material could be used by the enemy to incite violence against U.S. and Afghan service members,” he said in a statement.

The criticism was a departure for the Pentagon, which did not object publicly after news organizations posted the Marine urination video, nor when they published photographs of soldiers from another Army unit posing with corpses in 2010.

In the latest incident, the Times said it was given the graphic photographs by a soldier from the 82nd Airborne who wanted to expose “a breakdown in leadership and discipline that he believed compromised the safety of the troops.”

Times editor Davan Maharaj said he decided to publish two of the images as “a small but representative selection of the photos” to inform readers about important aspects of the military’s performance in Afghanistan.

George B. Wright Jr., an Army spokesman at the Pentagon, said the Army opened an investigation into the photographs in early March. He said the unit returned to the United States in 2010 and has since redeployed to Afghanistan.

It was not clear how many of the soldiers posing in the photographs are still with the unit, which the Times identified as the 1st Battalion, 508th Parachute Infantry Regiment.

Unit leadership concerns

U.S. commanders said they are investigating whether poor unit leadership by noncommissioned officers could have played a role in the recent cases of misconduct, amid concerns that troops have become desensitized or worn out after multiple deployments.

Sen. Jack Reed (D-R.I.), a former Army paratrooper who is on the Armed Services Committee, said one possible factor is a lack of direct supervision. Under the military’s counterinsurgency strategy, many small units are dispersed across rural parts of Afghanistan, often without their platoon leaders or company commanders.

“They aren’t always there, so they physically can’t exercise the leadership,” he said in an interview Wednesday.

Reed said the instances of misconduct are obscuring the military’s good deeds and effort to win the support of the Afghan people. “This is one of the difficulties of this kind of operation, with counterinsurgency,” he said. “It is as much a political battle as a tactical one.”

Andrew M. Exum, a former Army captain who served in Iraq and Afghanistan, said he doubted that the photos would cause a big stir among Afghans.

“Speaking bluntly, most Afghans are probably not going to be terribly offended by the body of a suicide bomber being treated in less-than-respectful ways,” said Exum, who is an analyst at the Center for a New American Security in Washington. Public reaction to the Marine urination video was relatively muted, he noted.

U.S. commanders pledged to disclose the results of their investigations of the Marine video, the Koran burning and the Kandahar massacre. So far, however, they have kept a tight lid on the probes and released few details.

In the United States, support for the war in Afghanistan is at an all-time low. A Washington Post-ABC News poll last week showed that only 30 percent of respondents say the war has been worth fighting.

Staff writer Greg Jaffe in Brussels and correspondent Kevin Sieff in Kabul contributed to this report.