Bekim Malaj and his friends knew they were fooling around with bombs, but they figured they were safe. After all, they reasoned, the bright yellow containers -- shaped like soda cans and topped with little parachutes -- had not exploded when they were dropped over Kosovo by NATO warplanes. They must be duds.

So the 10 young men and boys huddled near a wooden front gate in the village of Jahoc earlier this month to get a better look. One of them, a former Kosovo guerrilla who fancied himself an expert, pried open a canister.

"It started blowing fire," said Bekim, 11, lying half blind and heavily bandaged in a gloomy hospital bed here in this southwestern Kosovo city alongside victims of similar accidents. "It hit me in the face, and I started running, and then it blew up."

The young man who opened the bomb was "torn apart," in the words of one witness, and two others died along with him. Seven survivors were hospitalized, including two in critical condition.

Up to 170 people have been killed or injured over the past month in accidents involving land mines and unexploded bombs in Kosovo, according to a World Health Organization report released last week -- making Kosovo's casualty rate from those sources comparable to Afghanistan's and higher than that of Mozambique, where land mines from a civil war that ended six years ago still litter the countryside.

Just over half the Kosovo casualties were due to mines left by Serb-led Yugoslav troops, the WHO report said. But nearly as many have been caused by unexploded bombs dropped by U.S. and other NATO warplanes in their 78-day air offensive against Yugoslavia, the report said -- mostly from cluster bombs of the sort discovered by Bekim and his friends.

Tantalizing to children and potentially deadly if touched, cluster bomb explosives -- many of them painted bright yellow -- are smaller and more powerful than most land mines. The lightweight bomblets -- as many as 200 of which are bundled together in a single bomb casing, then carried to earth individually on tiny parachutes -- are often not easily recovered by disposal teams because of their tendency to drift off course or to become caught in trees, brush and roof fixtures.

The number of deaths and injuries from unexploded cluster munitions in Kosovo has reignited debate over their use and has prompted some U.S. officials to advocate that they be engineered to self-destruct if they land without detonating. The unexploded weapons also pose a serious threat to NATO peacekeeping troops now on patrol in Kosovo: Two British soldiers were killed last month as they tried to disarm one of the devices in a schoolyard.

"In my opinion, they pose the major threat right now," said Chris North, a 20-year British army veteran who is leading a Djakovica-based de-mining team for Handicap International, a French humanitarian group. "Most of the population here are aware of mines and know what they look like. But many don't know what cluster munitions look like, and that makes them a terrific risk. . . . If a person is nearby when one of them goes off, there's usually not much left."

Cluster canisters are fuzed to detonate within 50 feet of the ground; they can spray incendiary material to start fires, chunks of molten metal that can pierce tanks and other armor, or shrapnel that can slice with ease through 1/4-inch steel plate -- or human flesh and bone.

NATO officials say that about 1,100 cluster bombs, containing a total of more than 200,000 bomblets, were dropped on Yugoslavia and Kosovo, a province of Serbia, Yugoslavia's dominant republic. Their failure rate is about 5 percent. Human Rights Watch, a group that was sharply critical of their use during the air war, estimates that 11,000 unexploded cluster munitions of U.S. and British manufacture are scattered in the fields, trees and villages of Kosovo and the rest of Serbia, a number not disputed by NATO. The human rights group maintains that the weapons are unnecessarily dangerous to civilians, whether they explode as intended or drop to the ground.

"What worries us most is that people are going to start going back to work in the fields in the coming weeks, and so the numbers will almost certainly get higher," said Etienne Krug, who conducted the casualty survey for the World Health Organization.

U.S. and NATO officials acknowledge that unexploded cluster munitions pose a serious threat to civilians and troops but say they are working aggressively with U.N. agencies and other humanitarian organizations to identify and clear dangerous areas. On Friday, part of the road from Pristina, Kosovo's capital, to the western city of Pec was closed so explosives experts could detonate a NATO bomblet found next to the roadway.

"They are a particular concern to us because people may not be familiar with what they look like and what they can do," said Kevin Kennedy, spokesman for the U.N. mission in Kosovo. "People may not understand that they cannot be handled, just as mines cannot be handled."

U.S. officials say that while the danger from unexploded mines and air-dropped munitions in Yugoslavia is great, the situation is not as dire as in Kuwait and Iraq after the Persian Gulf War. According to figures compiled by Human Rights Watch, 1,200 Kuwaitis and 400 Iraqi civilians were killed by unexploded cluster canisters after the war; the group estimates that between 24 million and 30 million bomblets were dropped during the Gulf War, of which between 1.2 million and 1.5 million failed to explode.

In addition to NATO and the United Nations, about a dozen nonprofit groups have begun arriving in Kosovo to remove mines and bombs and to train civilians to help in the effort. About a fifth of all the mine and bomb victims documented by the World Health Organization were members of the Kosovo Liberation Army -- the ethnic Albanian rebel group that fought for independence from Serbia -- who were attempting to clear explosives from fields and villages without proper training.

At the dreary hospital here in Djakovica, where goats roam the grounds and patients are stacked eight to a room, nearly half the current caseload of 100 stems from mine and cluster bomb accidents. Western Kosovo was one of the most heavily bombarded and mined regions of the province.

Alfred Gjokaj, 20, also was showered with flame and shrapnel by the cluster bomb blast at Jahoc, but he survived and is now hospitalized. He can barely talk because of his swollen and torn face.

"We didn't know that they were dangerous," Gjokaj said. "We had seen those things opened before, and nothing has happened. We were figuring that they were not going to blow, after it didn't blow when it should."

His mother, File Gjokaj, shook her head in disgust as she stood by his bed. "There is still high danger here, even though the war is over," the woman said. "People just don't care when they see these types of devices. The kids will push them, shove them, all kinds of things. . . . I feel safe only in my yard -- and even then only in parts of the yard."

Staff writer Michael Dobbs in Washington contributed to this report.

Deadly Fragments of War

NATO dropped more than 1,000 cluster bombs over Serbia, including Kosovo, during the air campaign. They are particularly lethal because they scatter hundreds of smaller bomblets designed to pierce armor, kill personnel or start fires. Some of these bomblets did not explode and now pose a more serious danger than land mines left behind in Kosovo by Serb-led forces.

One of the cluster bombs widely used in NATO attacks over Serbia is the U.S.-made CBU-87/B. This thin-walled cylindrical weapon is dropped from attack aircraft, such as the F-16 (above).

The outer casing is set to open after several seconds of fall, or at a preset height above ground. The 202 bomblets inside are scattered over an area with a diameter affected by the spin of the casing as it falls. The faster the spin, the wider the area.

The bomblets are packed with different types of explosives to achieve various results:

Fragmentation bomblet: At detonation, the steel body of the bomblet disintegrates, dispersing 1-ounce fragments capable of injuring people 490 feet away.

Shaped charge/incendiary bomblet: This charge can pierce 4.9-inch-thick armor plate and includes a zirconium ring that creates burning particles that saturate the target, igniting fires from fuel sources.

SOURCE: Jane's Air-Launched Weapons