CAMP LEATHERNECK, Afghanistan — Defense Secretary Leon E. Panetta landed here Wednesday morning for an unannounced and tense visit, the first by a senior member of the Obama administration since an American soldier reportedly killed 16 Afghan civilians, mostly children and women. The two-day visit was planned months ago, but it has taken on a new urgency since an American staff sergeant slipped out of a military base in the southern province of Kandahar on Sunday and, according to villagers and senior defense officials, went door to door in nearby villages, shooting civilians.
“We will be challenged by our enemies, we will be challenged by ourselves, we will be challenged by the hell of war itself,” Mr. Panetta told some 200 Marines, Afghan security officers and troops from other coalition nations at this vast military base in the desert of Helmand Province, abutting Kandahar. Early in the day, a roadside bomb struck a minivan in Helmand at about 1 a.m., destroying the vehicle and killing eight civilians.
In a sign of the nervousness surrounding Mr. Panetta’s trip, the Marines and other troops who were waiting in a tent for the defense secretary to speak were abruptly asked by their commander to get up, place their weapons — M-16 and M-4 automatic rifles and 9-mm pistols — outside the tent and then return unarmed. The commander, Sgt. Maj. Brandon Hall, told reporters he was acting on orders from superiors.
“All I know is, I was told to get the weapons out,” he said. Asked why, he replied, “Somebody got itchy, that’s all I’ve got to say. Somebody got itchy; we just adjust.”
Normally, American forces in Afghanistan keep their weapons with them when the defense secretary visits and speaks to them. The Afghans in the tent waiting for Mr. Panetta were not armed to begin with, as is typical.
Later, American officials said that the top commander in Helmand, Maj. Gen. Mark Gurganus, had decided on Tuesday that no one would be armed while Mr. Panetta spoke to them, but the word did not reach those in charge in the tent until shortly before Mr. Panetta was due to arrive.
General Gurganus told reporters later that he wanted a consistent policy for everyone in the tent. “You’ve got one of the most important people in the world in the room,” he said. He insisted that his decision had nothing to do with the shooting on Sunday. “This is not a big deal,” he said.
Mr. Panetta, like President Obama, has denounced the killings and vowed to bring the killer to justice, a message he is to deliver in person to President Hamid Karzai of Afghanistan and top Afghan defense and interior officials while he is in Afghanistan. The killings have further clouded Afghan-American relations, which were already strained.
American commanders said that Helmand was relatively quiet after the killings, unlike Panjwai, the district in Kandahar where the rampage occurred. Militants there attacked a memorial service for the 16 victims on Tuesday when an Afghan government delegation was present, firing machine guns and assault rifles from their motorcycles and killing at least one Afghan soldier; a motorcycle bomb went off Wednesday near where the same delegation was staying in Kandahar city, killing a security officer.
Later on Wednesday, Mr. Panetta flew to a remote military base in western Helmand, Combat Outpost Shukvani, where American Marines fight alongside troops from Georgia, the former Soviet republic. The battalion commander of the 750 Georgian troops, Lt. Col. Alex Tugushi, lost both legs in a homemade bomb explosion in December; he is recovering at Bethesda Naval Hospital near Washington, where President Obama has visited him.
Mr. Panetta read a letter to the Georgians from Colonel Tugushi that said in part: “Unfortunately, I could not complete my service with you. But I am proud of all of you — those who have fallen and those who continue to serve. You are all heroes who will go down in Georgian history.”
Mr. Panetta told the troops in Helmand that the rampage on Sunday will not change the administration’s plans to withdraw 23,000 American troops from the country by the end of the summer and the remaining 68,000 by the end of 2014, although some could remain longer if the Afghans and Americas negotiate a long-term agreement.
Mr. Panetta told reporters on his plane on Monday that the killings in Panjwai were a horrific part of the decade-old conflict in Afghanistan.
“War is hell,” he said. “These kinds of events and incidents are going to take place, they’ve taken place in any war, they’re terrible events, and this is not the first of those events, and it probably will not be the last.” He added: “But we cannot allow these events to undermine our strategy.”