Yes. According to widespread media reports, images and analysis from credible experts, phosphorous weapons have been used in the conflict.

Let me begin by saying that there are fundamental rules stipulating that civilians must be protected from the effects of all military operations and that attacking civilians with any weapon is categorically prohibited.

The use of weapons containing white phosphorous is, like the use of any other weapon, regulated by the basic rules of international humanitarian law. These require parties to a conflict to discriminate between military objectives on the one hand and civilians and civilian objects on the other. The law also requires that they take all feasible precautions to prevent harm to civilians and civilian objects that can result from military operations. Attacks which cause "disproportionate" damage to civilians and to civilian objects are prohibited.

Using white phosphorous as an incendiary weapon, i.e. to set fire to military targets, is subject to further restrictions. The use of such white phosphorous weapons against any military objective within concentrations of civilians is prohibited unless the military objective is clearly separated from the civilians. The use of air-dropped incendiary weapons against military objectives within a concentration of civilians is simply prohibited. These prohibitions are contained in Protocol III of the Convention on Certain Conventional Weapons.

In addition, customary international humanitarian law, which is applicable to all parties to any conflict, requires that particular care must be taken when attacking a military target with incendiary weapons containing white phosphorous, in order to avoid harm to civilians and damage to civilian objects. If this substance is used against fighters, the party using it is obliged to assess whether a less harmful weapon can be used to put the fighters out of action.

If munitions containing white phosphorous are used to mark military targets or to spread smoke then their use is regulated by the basic rules of international humanitarian law.

The fact that international humanitarian law does not specifically prohibit phosphorous weapons does not imply that any specific use of weapons containing this substance is legal. The legality of each incident of use has to be considered in light of all of the fundamental rules I have mentioned. It may be legal or not, depending on a variety of factors.

If ICRC delegates in the field gather credible and precise evidence of violations, or if ICRC medical personnel corroborate reports by others, the ICRC would begin by discussing this with the party concerned – rather than speaking publicly – in keeping with our standard practices. We have not commented publicly on the legality of the current use of phosphorous weapons by Israel, contrary to what has been attributed to us in recent media reports.

Yes. White phosphorous weapons spread burning phosphorous, which burns at over 800 degrees centigrade (about 1,500 degrees fahrenheit), over a wide area, up to several hundred square metres. The burning will continue until the phosphorous has been completely depleted or until it no longer is exposed to oxygen. The weapon has a potential to cause particularly horrific and painful injuries or slow painful death. Medical personnel must be specially trained to treat such injuries and may themselves be exposed to phosphorous burns. If used against military targets in or near populated areas, weapons containing this substance must be used with extreme caution to prevent civilian casualties.

See also Customary rules of IHL