WASHINGTON -- The Pentagon acknowledged yesterday that it used white phosphorus munitions in a 2004 offensive in the Iraqi city of Fallujah, but said the weapon is legal and denied that the US military had targeted civilians with the highly flammable substance.
Pentagon officials said that US troops had employed it against insurgent strongholds as an incendiary weapon. But they continued to deny a report on Italian state television last week alleging that the munitions had been used against civilian men, women, and children in Fallujah, some of whom were burned to the bone.
''We categorically deny that claim," said Army Lieutenant Colonel Barry Venable, a Pentagon spokesman.
Some critics have argued that the use of white phosphorus in Fallujah constituted a chemical weapons attack prohibited by the international chemical weapons convention, to which the United States is a signatory.
But Venable said white phosphorus is not outlawed and said it is not covered by the convention on chemical weapons.
A protocol to a 1980 accord on conventional weapons that took effect in 1983 forbids using incendiary weapons against civilians. The protocol also forbids their use against military targets within concentrations of civilians, except when the targets are clearly separated from civilians and ''all feasible precautions" are taken to avoid civilian casualties.
The United States is a party to the overall accord, but has not ratified the incendiary-weapons protocol or another involving blinding laser weapons.
Another Pentagon spokesman, Bryan Whitman, said of white phosphorus: ''It's part of our conventional-weapons inventory and we use it like we use any other conventional weapon."
White-phosphorus munitions are primarily used by the US military to make smoke screens and illuminate targets, but are also employed as an incendiary weapon against enemy combatants, the Pentagon said. The substance ignites easily in air at temperatures of about 86 degrees and its fire can be difficult to extinguish. It can cause painful burn injuries to exposed human flesh.
US forces used the white phosphorus during a major offensive launched by Marines in Fallujah, about 30 miles west of Baghdad, to flush out insurgents. The battle last November involved some of the toughest urban fighting of the 2 1/2-year war.
Venable said that in the Fallujah battle, ''US forces used white phosphorus both in its classic screening mechanism and . . . when they encountered insurgents who were in foxholes and other covered positions who they could not dislodge any other way."
He said the soldiers employed what they call a ''shake-and-bake" technique of using white- phosphorus shells to flush enemies out of hiding, and then using high explosives to kill them.
The Italian documentary showed images of bodies recovered after the Fallujah offensive, which it said proved the use of white phosphorus against civilians, but the military denied the allegations.
''We don't target any civilians with any of our weapons. And to suggest that US forces were targeting civilians with these weapons would simply be wrong," Whitman said yesterday.
An Iraqi human rights team was heading to Fallujah yesterday to investigate the US forces' use of white phosphorus as a weapon, Iraq's acting human rights minister told the BBC.
Minister Narmin Uthman said her team plans to investigate whether civilians were affected by the substance.
Daryl Kimball, executive director of the Washington-based Arms Control Association, questioned whether the US military was using the weapons in a manner consistent with the conventional weapons convention.
''White phosphorous weapons should not be used just like any other conventional weapon," Kimball said. He called for an independent review of how the United States was using the weapons and possibly an investigation by countries that are parties to the convention ''to determine whether their use in Iraq is appropriate or not."
The BBC quoted Peter Kaiser, spokesman for the Organization for the Prohibition of Chemical Weapons, based in The Hague, as saying that the use of white phosphorus as a toxic or caustic agent would make it illegal under the chemical weapons convention. The Pentagon contends that it uses the weapon for its incendiary heat and not for toxic properties.
In London, the British government said yesterday that its military uses white phosphorus in Iraq but only to lay smoke screens.
Prime Minister Tony Blair's official spokesman refused to be drawn in on the claims that US troops have used white phosphorous against civilians.
''Use of phosphorus by the US is a matter for the US," the spokesman told reporters in a briefing, speaking on condition of anonymity because he was not authorized to have his name published. Blair's spokesman pointed out that Britain is a signatory to Protocol III of the 1980 Convention on Conventional Weapons.
Britain's Liberal Democrat Party, which opposed the Iraq war, criticized US forces for using the substance as an incendiary weapon.
''A vital part of the effort in Iraq is to win the battle for hearts and minds," said the party's foreign affairs spokesman, Menzies Campbell. ''The use of this weapon may technically have been legal, but its effects are such that it will hand a propaganda victory to the insurgency."
Material from the Associated Press was included in this report.