They're blowing up Beirut again. But now it is for the sake of peace.

A soldier stops traffic at the edge of the Green Line, once a killing zone but now a ruined, haunting reminder of 15 years of civil war."Get out of your cars and stand away from the buildings," he commands. "Pieces may fall off."

Two shots ring out - a warning signal.

"Now put your hands over your ears and watch out," says the soldier, swiftly following his own orders. "It won't take long."

Seconds later a mine explodes, destroying a two-story shop. The blast throws stone blocks across Martyrs' Square.

A child screams. The soldier and the now-dusty civilians smile.

In Beirut, at least this month, peace is a controlled explosion and no casualties.

Troops are clearing mines and shells on the Green Line, an eight-mile swath of streets splitting Moslem West Beirut from the Christian east.

The Green Line is the oldest and bloodiest frontline in Lebanon's civil war, which has claimed about 150,000 lives since 1975.

No one knows how many people died on the Green Line in the dozens of blocks of wrecked banks, markets, cafes and nightclubs around Martyrs' Square in the abandoned heart of Beirut.

Reaching Martyrs' Square, once an international oasis for pleasure and high finance, is like stepping back in time to the prewar beauty of Beirut - but despoiled by savagery.

The elegant rectangular square is now divided by dirt barricades reinforced with upturned cars, buses and shipping containers.

Mines and shells unsafe to move are blown up on the spot by the troops who took over Beirut and its suburbs in early December after Moslem and Christian militiamen pulled out.

Bulldozers then scoop up the debris of concrete and dirt ramparts and mow down thick undergrowth and trees, which turned downtown Beirut into a dangerous and unruly park.

Thousands of mines stud the Green Line. They range from plastic hand-sized anti-personnel weapons triggered by tripwires to drums filled with explosives set to wreck tanks.

The mines and shells echo the traditional international tone of this city. Most were made in the United States, the Soviet Union, Israel, Italy or eastern Europe.

"We've found 600 mines in this area in three days, but there are hundreds more," said an army lieutenant from the mainly Moslem Sixth Brigade as the smoke cleared from the latest detonation. "It's a hard task. We have to search everywhere to be safe."

He estimated that the cleanup would take three weeks before all roads in the Martyrs' Square area were open to traffic. The army warns civilians against visiting until then.

Despite the warnings, scores of people arrive on foot each day to inspect what is left of their houses or businesses. Most are elderly.

"Nothing, nothing," said a shocked old man, who was near tears as he gazed at the ruins of his pharmacy on the square. He last dared to visit his shop six years ago, although he lives only 200 yards away.