By Jacques Clement

GAZA, Jan 23, 2009 (AFP) - For Amnesty International the evidence was all there: a hole in a burnt-out ceiling, fragments of a shell -- and a substance that bursts into flames at the slightest contact.

White phosphorus is an incendiary weapon, but in civilian areas it is banned under an international convention.

Amnesty is investigating its use by the Israeli military during a 22-day assault against the Islamist movement Hamas in the Gaza Strip.

On Monday, January 5, Israeli artillery bombarded the outskirts of Beit Lahiya town in the northern Gaza Strip.

Sabah Abu Halima and her family rushed to the top floor of their house, to shelter in a corridor without windows and escape any flying glass.

Two weeks later in the same location, Chris Cobb-Smith, a British weapons expert, recounts what happened next:

"Here the white phosphorus comes through the roof, detonates as it hits the wall and distributes the pieces of white phosphorus within the house, and that's the explanation for the severe burning that you see around," he says.

Since last weekend, Cobb-Smith has criss-crossed the Gaza Strip with an Amnesty delegation investigating the Israeli army's use of phosphorous bombs, which burst into flames on contact with oxygen.

Such weapons are regulated by the 1980 Convention on Certain Conventional Weapons, more specifically by Protocol III on Prohibitions or Restrictions on the Use of Incendiary Weapons, which bans them in civilian areas.

Five civilians were killed and four wounded, including Sabah Abu Halima herself, when her Beit Lahiya home was hit.

"It hurts me terribly, my skin is burning. I don't sleep any more, neither day nor night," she said in the burns unit of Gaza's Shifa hospital. Halima may be evacuated to Egypt along with the three other members of her family who were wounded.

Gaza hospitals have been inundated with victims of white phosphorus, which they don't know how to treat as the substance "has never been used in the Gaza Strip," says Elizabeth Hodgkin, who worked as a Middle East researcher for Amnesty from 1994 to 2002.

At Shifa hospital, survivors recount how their wounds began smoking when they washed them or took off their bandages, as white phosphorus remains active for a long time and continues to burn when you try to smother it.

It explodes on contact with the air and is used by armies mainly to create a smokescreen or to mark targets for aerial bombardment, says Cobb-Smith, a former British army soldier.

"There is absolutely no military, tactical reason for the use of white phosphorus in this environment," he says.

"I believe it's just being purely used as a weapon of terror to frighten, to intimidate people. Obviously it's going to cause physical harm as well because it can kill people and it can destroy property."

Amnesty, which considers its use in heavily-populated areas a war crime, has found many phosphorous particles in civilian areas, including Gaza's Al-Quds hospital, says Donatella Rovera, the head of the Amnesty team.

She called for an investigation by the United Nations into alleged crimes committed by both sides in the Gaza war.

Eventual sanctions would depend "on the political will of the countries which have influence, essentially the United States and the European Union," Rovera says.

Israel has not denied using white phosphorus but at the same says that it does not use weapons banned by international conventions.

However, the liberal Israeli newspaper Haaretz said the army was investigating the possible use of a phosphorous shell in Beit Lahiya.

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