Ian Collins died from massive head injuries

Macedonian police said the teenagers would be charged with committing serious acts against public security, a charge between manslaughter and murder in gravity.

In quoting sources in the Macedonian judiciary the BBC's Paul Anderson in Skopje said the youths had admitted playing a stupid game when they dropped a block of concrete on to the convoy from a bridge on the outskirts of the capital.

Sapper Collins, a 20-year old Royal Engineer, died from head injuries despite attempts to save him, first at an American base in Kosovo, then at a hospital in Skopje.

The death on 27 August came soon after the British-led force arrived in Macedonia for operation Essential Harvest, shocked the Nato brigade.

Mission hailed success

Nato spokesman Mark Laity said: "Obviously we are very satisfied that the Skopje police appear to have reached a successful conclusion to this sad and tragic case."

The Nato mission is now being deemed a success.

Most of the targeted weapons have been collected allowing 4,500 Alliance troops, more than a third of them British, to begin pulling out next week.

A small follow-on force will stay to protect international peace monitors.