The US has now admitted using white phosphorus as a weapon in Falluja last year, after earlier denying it.
White phosphorus is highly flammable and ignites on contact with oxygen. If the substance hits a person's body, it will burn until deprived of oxygen. Globalsecurity.org, a defence website, says: "Phosphorus burns on the skin are deep and painful... These weapons are particularly nasty because white phosphorus continues to burn until it disappears... it could burn right down to the bone."
Washington is not a signatory to an international treaty restricting the use of the substance against civilians.
- Professor Paul Rodgers, of the University of Bradford's department of peace studies, said white phosphorus could be considered a chemical weapon if deliberately aimed at civilians. "It is not counted under the chemical weapons convention in its normal use but, although it is a matter of legal niceties, it probably does fall into the category of chemical weapons if it is used for this kind of purpose directly against people."