Nato should dispose of large fragments of depleted uranium (DU) ammunition remaining in Kosovo 18 months after the conflict ended, because they represent an unnecessary risk to health, a UN study says.

Further details of the preliminary results of the UN Environment Programme investigation emerged yesterday as the EU began an inquiry into whether there is a link between radioactive military debris and the death from cancer of soldiers who served in the Balkans.

Meanwhile, the European commission president, Romano Prodi, called for DU-coated shells to be banned, after the French defence ministry said that four French soldiers who served in the Balkans during Nato's bombing of Yugoslavia in 1999 were being treated for leukaemia in a military hospital.

"It is clear that if there is even a minimal risk, these arms must be abolished," he said. "And even if this risk was not there, I don't like the idea of using these particular weapons".

Britain remains one of the few countries to resist compulsory screening of troops returning from Kosovo for traces of contamination. The ministry of defence insisted that in its solid form was not a health hazard. "The UN's initial findings were that there were a lot of other things which were of far greater concern," a spokesman said.

Italy opened an inquiry last week into a possible link between DU and 30 cases of serious illness in troops who served in the area, 12 of whom developed cancer. Five have already died of leukaemia.

The Campaign Against Depleted Uranium in Manchester says that most of the areas where DU shells were dropped during the Kosovo war are in the south, in the Italian sector.

Spain said it would examine all the 32,000 soldiers who have served in the Balkans since 1992. Portugal, Finland, Turkey, Bulgaria and Greece also plan to screen their peacekeepers and check radiation levels to discover if there is such a condition as "Balkans syndrome".

The biologist leading the Royal Society's inquiry into the long-term effects of DU weapons, Professor Brian Spratt of Oxford University, called on the government to test British troops.

"The leukaemia cases are probably not related, but the health of soldiers who go out to fight for their country should be taken seriously," he said.

In its preliminary statement, the UN said it had found "slightly higher" radioactivity in Kosovo at eight of the 11 sites examined last November. Nato had given details of 112 sites where an estimated 31,000 rounds of armour-piercing DU ammunition were used during attacks on Serb targets.

A US army officer on the team, who helped develop DU ammunition, was apparently surprised to find that it had not vapourised or dispersed.

The UN statement said that its scientists had found "either slightly higher amounts of Beta-radiation, specifically at or around the holes left by DU ammunition, or remnants of ammunitions, such as sabots and penetrators".

The team collected seven DU outer casings and seven penetrators.

"It is an extra risk for the population, and that is something that military experts were surprised to find," Pekka Haavisto, the Finnish head of the mission, said yesterday.

There is also concern about mine clearance, because most DU was found in heavily mined areas or sites with unexploded ordinance - some of which is cleared by controlled explosions. The UN believes this can turn DU back into its most dangerous form - a dust that can be inhaled.