Bosnia's Big Bang alarms the mayor

Loud explosions, each produced by four tons of high explosive, echoed across the quiet farmland of Serb controlled Bosnia yesterday. A chocolate-brown mushroom cloud, turning white at the top, soared 5,000 feet into the air. Even two miles away, the blast, filtered down the valley, ruffled the canopy on the back of a British army four ton truck before the sound was heard.

In the face of growing confrontation with the local Serbs, the peace implementation force (I-For) was continuing its Operation Volcano, the destruction of an astonishing 400 tons of munitions found in an unauthorised Serb arms dump in the old schoolhouse at Margetici, 25 miles east of Sarajevo. Yesterday the local mayor demanded - and got - discussions with Lieutenant General Sir Michael Walker, commander of Nato troops in Bosnia and deputy commander of I-for.

To ensure nothing went wrong, 2,000 I-For troops- mostly French and Italians, with some British and Portuguese - had been deployed to secure the area, transport the offending ammunition, ensure the evacuation of people and animals, and construct the excavations for its destruction.

Such detonations are taking place three times a day, and the local people are not happy. Milan Tupajic, the tough-looking mayor of Sokolac, the nearest town five miles to the west, arrived at the press conference organised by I-For to put his side of the story. On Monday, Mr Tupajic said the explosions at one of the two prepared sites had to stop because they would damage a deep underground aquifer which is important to the area's water supply. I-For immediately stopped detonations at the site in question, the more westerly site 1.

But yesterday it continued to destroy the ammunition - anti-tank and anti-personnel mines, plastic explosives and small-arms ammunition - at site 2, two km north-east. Mr Tupajic was controlled but clearly determined. "Site 2 is in the same area," he said. "The water in one place is in the other place three hours later. I am an engineer but I am not a specialist. But you are soldiers. There are no geologists or hydrologists involved. I appeal to you again to postpone this operation."

I-For officers at the scene yesterday were flabbergasted that the Serbs would keep so much ammunition in such a place as a schoolhouse. "Four tons makes a hole seven metres deep and 24 metres across," said Lt-Col Max Marriner, a senior I-For spokesman. "Imagine what would happen if all 400 tons had gone off at once on the edge of a village."

General Walker said the unauthorised ammunition dump was by far the largest found in Bosnia. For comparison, 3,600 tons was held in declared sites. The offence, he said, was "compounded by many violations", and for that reason I-For had decided to confiscate it and destroy it.

Three miles up a track, the Italians and French had prepared the six holes for the new blast in Operation Volcano. A hole at least two metres deep was dug, although old pits were also used. The area within a kilometre of the blasts had be cleared of people and animals. "We had some trouble with cows and sheep," said the French expert in charge of the detonations. "But they obeyed us, and went away."