KABUL — Perhaps no action is as guaranteed to provoke a furious reaction from Afghans as desecration of the Quran. But in what military officials described as a horrifying mix-up, U.S. troops apparently sent copies of the Muslim holy book to the trash-disposal “burn pit” at a sprawling base north of the capital.

Within hours, hundreds of angry protesters had gathered at the gates of Bagram Airfield, and the American general who commands Western troops in Afghanistan issued an emphatic apology, promising such an event would never be repeated.

The incident, coming weeks after a video surfaced of U.S. Marines urinating on the corpses of slain Taliban fighters, is likely to inflame anti-American sentiment at a sensitive time. The Obama administration is trying to enlist Afghan President Hamid Karzai’s help in starting peace talks with the Taliban and in reaching an accord on a long-term American presence in Afghanistan.

The Taliban movement issued a statement denouncing the Quran incident as a “barbarous act” and calling it one of many by Western “invaders.”

In Tuesday’s protest, guards at the base fired rubber bullets and tear gas after a stone-throwing, chanting crowd swelled to 1,000, witnesses said.

Bagram district police chief Abdul Aziz said the incident began before dawn when a group of Afghans working as laborers inside the base saw copies of the Quran at the burn pit and carried them outside.

It was unclear how many copies of the holy book, if any, were burned. Ahmad Zaki Zahid, the chairman of the provincial council in Parwan, where the base is located, said about 60 copies of the Quran were taken to the incinerator after being left behind by freed detainees, and about half were burned and half were retrieved.

U.S. Marine Corps Gen. John Allen’s statement was unusually rapid and strikingly contrite.

Addressing the “noble people of Afghanistan” in a video that was aired on national television, Allen said he had been given a report overnight indicating that Western military personnel at Bagram had “improperly disposed of a large number of Islamic religious materials,” including Qurans.

“We are thoroughly investigating the incident and we are taking steps to ensure this does not ever happen again,” Allen said. “This was not intentional in any way.”