Some military experts say video of the Israeli assault on Gaza may show the use of phosphorus shells over Gaza City.
If true, use of the weapons in a densely populated area would contravene international laws.
Burning phosphorus causes severe and possibly fatal burns when it comes into contact with human skin. Israel has flatly denied using the lethal weapon.
An Israeli military spokeswoman insisted that all ammunition being used is in accordance with international law.
A senior military analyst at Human Rights Watch says the Israeli Defence Forces have confirmed they are using white phosphorus in Gaza to hide troop movements a legal, non-lethal use of the substance.
Israel has a recent history of using phosphorus during conflict including during the 2006 war in Lebanon.
(CCTV January 7, 2009)
