WASHINGTON — Pentagon officials acknowledged Tuesday that U.S. troops used white phosphorus as a weapon against insurgent strongholds during the battle of Fallujah last November. But they denied an Italian television news report that the spontaneously flammable material was used against civilians.

Lt. Col. Barry Venable, a Pentagon spokesman, said that while white phosphorus is most frequently used to mark targets or obscure a position, it was used at times in Fallujah as an incendiary weapon against enemy combatants.

"It was not used against civilians," Venable said.

The spokesman referred reporters to an article in the March-April 2005 edition of the Army's Field Artillery magazine, an official publication, in which veterans of the Fallujah fight spelled out their use of white phosphorus and other weapons. The authors used the shorthand "WP" in referring to white phosphorus.

"WP proved to be an effective and versatile munition," the authors wrote. "We used it for screening missions at two breeches and, later in the fight, as a potent psychological weapon against the insurgents in trench lines and spider holes when we could not get effects on them with HE (high explosive)" munitions.

"We fired 'shake and bake' missions at the insurgents, using WP to flush them out and HE to take them out."

The authors added, in citing lessons for future urban battles, that fire-support teams should have used another type of smoke bomb for screening missions in Fallujah "and saved our WP for lethal missions."

The battle for Fallujah was the most intense and deadly fight of the war, after the fall of Baghdad in April 2003. The city was a key insurgent stronghold. The authors of the "after action" report said they encountered few civilians.

Italy's state-run RAI24 news television aired a documentary last week alleging the U.S. used white phosphorus shells in a "massive and indiscriminate way" against civilians during the Fallujah offensive.

The State Department, in response, initially denied that U.S. troops had used white phosphorus against enemy forces. "They were fired into the air to illuminate enemy positions at night, not at enemy fighters."

The department later said its statement had been incorrect.

"There is a great deal of misinformation feeding on itself about U.S. forces allegedly using 'outlawed' weapons in Fallujah," the department said. "The facts are that U.S. forces are not using any illegal weapons in Fallujah or anywhere else in Iraq."

Venable said white phosphorus shells are a standard weapon used by field artillery units and are not banned by any international weapons convention to which the U.S. is a signatory.

White phosphorus is a colorless-to-yellow substance with a pungent odor. The form used by the military ignites once it is exposed to oxygen, producing such heat that it bursts into yellow flame and produces a dense white smoke. It can cause painful burns.

The Italian documentary quoted ex-Marine Jeff Englehart, who was identified as attached to the U.S. 1st Infantry Division in Iraq, as saying he saw the bodies of burned children and women after the bombardments.

"Burned bodies. Burned children and burned women. White phosphorus kills indiscriminately. It's a cloud that, within ... 150 meters of impact, will disperse and will burn every human being or animal."

The documentary showed images of bodies recovered after the Fallujah offensive, which aimed to crush followers of insurgent leader Abu Musab al-Zarqawi, said to have linked with local insurgents in the Sunni Arab city.