FACTBOX: Key facts about white phosphorus munitions

(Reuters) - Shells containing white phosphorus have severely burned an 8-year-old Afghan girl, according to U.S. military doctors who treated her.

The girl, Razia, is the first reported civilian casualty from the chemical in Afghanistan.

Following are key facts about white phosphorus:

MILITARY APPLICATIONS

White phosphorus munitions can be used on battlefields to make smoke screens, generate illumination, mark targets or burn bunkers and buildings.

Because it has legal uses, white phosphorus is not banned as a chemical weapon under international conventions. But some U.S. military training manuals say its use against people is banned.

It is a colorless or yellowish translucent wax-like substance that smells a bit like garlic and ignites on contact with oxygen. Its fire is difficult to extinguish, and it sticks to flesh, making its burns more severe. "Infection is common and the body's absorption of the chemical can cause serious damage to internal organs, as well as death," Human Rights Watch says.

INTERNATIONAL LAW

Under international law, white phosphorus is considered an incendiary weapon, defined by Protocol III of the Convention on the Prohibition of Use of Certain Conventional Weapons as "any weapon or munition which is primarily designed to set fire to objects or to cause burn injury to persons through the action of flame, heat or combination thereof, produced by a chemical reaction of a substance delivered on the target."

The protocol prohibits using incendiary weapons against military targets located among civilians, although the United States has not signed it and is not bound by it. According to Human Rights Watch, "customary laws of war also prohibit the anti-personnel use of incendiary weapons so long as weapons less likely to cause unnecessary suffering are available."

USED BY U.S. MILITARY IN IRAQ AND AFGHANISTAN

The Pentagon acknowledged the use of white phosphorus munitions in the November 2004 Marine-led offensive in the Iraqi city of Falluja that involved fierce urban fighting.

Shells containing white phosphorus were fired at insurgents in foxholes or other covered positions to smoke them out, and they were then hit with high-explosive artillery rounds in what troops called the "shake and bake" technique.

Colonel Gregory Julian, spokesman for the commander of U.S. and NATO forces in Afghanistan, said foreign troops in the country use white phosphorus munitions for illumination and as an incendiary to destroy enemy equipment and bunkers.

White phosphorous is often described by the military as "Whiskey Pete" or "Willy Pete."

(Reporting by Jerusalem and Kabul newsrooms; Editing by Paul Tait)