Dozens of Afghan reporters, distraught over the death of Mr. Ahmad, pledged to embark on a 15-day boycott of all news related to the Taliban, though it was unclear how it would work in a country where insurgency looms over many aspects of life.

Zabiullah Mujahid, a Taliban spokesman, claimed the children were not executed but were killed in crossfire. He insisted that the Taliban was not responsible for their deaths, and that Mr. Ahmad was an unintended victim, not a target, of the attack.

Still, he sought to justify the deaths as unfortunate casualties in an “unbalanced war” where air strikes by the American-led coalition have killed Afghan civilians. But “there is no acceptable way to defend the deaths of these children, and we regret their deaths,” he said in telephone an interview, as a child squealed in background.

Seddiq Seddiqi, the Interior Ministry spokesman, told reporters the young insurgents managed to sneak guns past the hotel guards and metal detectors by hiding them in their socks and wrapping them in plastic. He did not explain how the plastic would have shielded the guns from detection, and also suggested that the assailants may have had inside help.

Regardless of how they slipped past security, by the time they walked across the stone driveway and into the lobby, they appeared ready to celebrate, hotel staff said in interviews on Friday. Wearing trimmed beards and smart clothes, they told staff they planned to mark the Persian New Year in the hotel’s elegant dining room, where patrons enjoy nightly buffets of Western and Afghan fare.

But first they wandered around the Serena for a while, staff recalled, taking in its opulence, which differs starkly from the homes that even prosperous Afghans live in, never mind the mud hovels of the poor villagers from which the insurgent draw most of their fighters.