ITALY, Rome -- NATO's use of depleted uranium could be investigated as a possible war crime, the chief prosecutor for the international war crimes tribunal has said.

Carla del Pronte told Italian state TV on Sunday: "If we have sufficient elements we will be obliged to investigate" as to whether the use of the heavy metal in the Balkans conflicts constituted a war crime.

Numerous NATO member states, including Italy, are currently carrying out their own health and scientific investigations into a possible link between the use of the radioactive weapons used during the Balkan wars and cancer-related deaths among servicemen serving in the region.

The latest country to embark on an investigation is Switzerland. Its defence ministry said on Sunday it planned to check the health implications of DU weapons test-fired in central Switzerland 30 years ago.

Del Pronte added in another interview, published by Corriere della Sera on Sunday, that the tribunal had already looked into the use of the controversial ammunition during NATO's 1999 campaign in Kosovo "but we didn't have enough elements to proceed."

DU, used in the tips of missiles, shells and bullets to boost their ability to penetrate armour can be turned on impact into a toxic radioactive dust, defence experts say.

Doctor Zoran Stankovic, head of the department of forensic medicine of the Yugoslav Military-Medical Academy in Belgrade, said he has discovered a connection between the weapons and 400 cancer deaths among Bosnian Serbs.

Many of the Serbs from Hadzici had worked in a factory repairing tanks and armoured vehicles that were heavily bombed by NATO in 1994.

At the time, DU shells found on the ground were recycled and used to produce flack jackets.

He said no organised study had been launched to establish links between DU and health hazards, but added he strongly felt the link existed.

Russia has called for an international conference of specialists to look at the problem within the Organization for Security and Co-operation in Europe (OSCE), the Interfax news agency quoted Defence Minister Igor Sergeyev as saying.

Switzerland's defence ministry spokesman Oswald Sigg was quoted in SonntasgBlick newspaper on Sunday as saying it would have to "investigate immediately" the results of test firing by a weapons company in the 1970s.

Sigg said the government was aware of only one test at one Swiss firing range. "We're checking to see if other places were used," he said.

"We fired uranium ammunition at our Ochsenboden firing range near Studen," in the canton (state) of Schwyz, the paper quoted Heinrich Meier, former head of the Oerlikon Contraves munitions factory that conducted the test, as saying.

The firing range is now a golf course.

The paper cited a local environmental official as saying the area was tested for heavy metals but not for radioactivity before the course opened.

Swiss military officials have played down the health risk of DU ammunition for peacekeeping troops who served in the former Yugoslavia, but have offered blood tests to any soldiers or civilian aid workers who want them.

One Swiss officer who served in Bosnia in 1998 has died of leukaemia, but the army surgeon general has said it would be practically impossible to establish that radiation from DU ammunition had caused or contributed to the illness.

NATO says the ammunition poses a negligible health hazard, and the World Health Organisation, says it is unlikely that exposure to DU ammunition could have led to a higher risk of cancer among soldiers in the Balkans.

But deaths from leukaemia among peacekeepers are under the spotlight after reports that six Italian soldiers who served in the Balkans had developed the illness.

U.S. attack jets fired 31,000 rounds of DU ammunition against Serbian targets during NATO's 1999 campaign to drive the Yugoslav army out of Kosovo.

Some 10,000 rounds were fired in neighbouring Bosnia in 1994-95.

The Associated Press & Reuters contributed to this report.