WASHINGTON (Reuters) - The Pentagon on Wednesday acknowledged using incendiary white-phosphorus munitions in a 2004 offensive against insurgents in the Iraqi city of Falluja and defended their use as legal, amid concerns by arms control advocates. Army Lt. Col. Barry Venable, a Pentagon spokesman, said the U.S. military had not used the highly flammable weapons against civilians, contrary to an Italian state television report this month that stated the munitions were used against men, women and children in Falluja who were burned to the bone. "We categorically deny that claim," Venable said. "It's part of our conventional-weapons inventory and we use it like we use any other conventional weapon," added Bryan Whitman, another Pentagon spokesman. Venable said white phosphorus weapons are not outlawed or banned by any convention. However, a protocol to an accord on conventional weapons which 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. White phosphorus munitions are primarily used by the U.S. military to make smoke screens and mark targets, but also as an incendiary weapon, the Pentagon said. They are not considered chemical weapons. The substance ignites easily in air at temperatures of about 86 degrees F (30 C), and its fire can be difficult to extinguish. 'APPROPRIATE OR NOT' Daryl Kimball, executive director of the Washington-based Arms Control Association, questioned whether the U.S. 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. Kimball 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." U.S. forces used the white phosphorus during a major offensive launched by Marines in Falluja, about 30 miles (50 km) west of Baghdad, to flush out insurgents. The battle in November of last year involved some of the toughest urban fighting of the 2-1/2-year war. Venable said that in the Falluja battle, "U.S. forces used white phosphorous 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 a "Shake and bake " technique of using white phosphorus shells to flush enemies out of hiding and then use high explosives artillery rounds to kill them. The Italian documentary showed images of bodies recovered after the Falluja offensive, which it said proved the use of white phosphorus against civilians. "We don't target any civilians with any of our weapons. And to suggest that U.S. forces were targeting civilians with these weapons would simply be wrong," Whitman said. "Shake and bake "