KABUL, Afghanistan -- Afghanistan's spy chief, Asadullah Khalid, was taking no chances.
A man had crossed into Afghanistan from Pakistan with important information he said he would only deliver personally to Mr. Khalid, who had just taken over as the head of the National Directorate of Security.
Mr. Khalid's aides took the visitor to an armored room in the basement of a safe house in Taimani, an upscale neighborhood in the capital city, for a security screening. They were no doubt mindful of what happened in September 2011 when a Taliban peace emissary was allowed to meet with a prominent Afghan peace envoy and then killed him with a bomb hidden in his turban.
Watching the man over closed-circuit television, they ordered him to strip naked, which he did. Satisfied, they let him get dressed and took him to see their boss upstairs.
Then he blew up. The suicide bomber killed only himself, but Mr. Khalid sustained severe abdominal wounds as well as injuries to his hands and arms.
Now, months after that attack, on Dec. 6, a spokesman for the National Directorate of Security, Shafiqullah Tahiri, confirmed that the attacker had hidden the bomb inside his rectum.
Two other Afghan security officials, speaking on the condition of anonymity, confirmed that the bomb had been hidden internally. Officials had earlier been quoted as saying the bomb had been hidden in the attacker's underwear.
The last time such a bomb was known to be used was in an attempt to kill a Saudi prince with a device thought to be the work of Ibrahim Hassan al-Asiri, one of the most skilled bomb makers of Al Qaeda's Yemen affiliate.
In August 2009, Mr. Asiri's brother, Abdullah, detonated himself during a meeting with Prince Muhammad bin Nayef, the deputy interior minister at the time, in Jidda. The prince was only lightly wounded; the bomber's lower torso was shredded.
Afterward, the counterterrorism unit of Europol, Europe's police agency, warned that airlines might have to tighten their screening procedures because a rectal bomb could escape detection by normal X-ray scanning machines.
"The sensitivity and power of these machines would need to be increased or reviewed, in order to overcome shielding of the device by the human body," Europol's report said.
Mr. Asiri, who was linked to the Saudi attack by postings on jihadist Web sites, is also believed to be the creator of the underwear bomb, used in an abortive attempt to bring down an American airliner in 2009.
Despite the concerns about what such bombs could accomplish on an airplane, and that they might make it easier to evade detection by normal X-ray scanners, Robert Bunker, a researcher who has extensively studied the possibilities of body-cavity suicide bombs, noted that there were inherent limitations to the design.
"There are some really practical limitations to what you can do with the basic physics," he said. "You can only get so much in the body, and there is no shrapnel effect." Because they are so small, the blast is greatly blunted by the bomber's body itself.
"It's good news that these things have very limited lethality," Mr. Bunker said.
The origin and exact design of the bomb used against Mr. Khalid remained unclear. Within days of the attack, Mr. Khalid was taken to Walter Reed National Military Medical Center, a leading treatment site for blast injuries. Though he returned to Kabul on April 2, within weeks he was back at Walter Reed for treatment of complications, and he apparently remains there.
The Taliban claimed responsibility for the attack on Mr. Khalid, but when asked whether it had been done with a body-cavity bomb, a Taliban spokesman, Zabiullah Mujahid, demurred. "There is a commission in the Islamic Emirate that is organizing and masterminding these sophisticated and complicated operations," he said. "We can't reveal the secret because we may use these tactics again in the future."
This article originally appeared in The New York Times.