Refugee Camp in Bosnia Attacked : Balkans: Serbs are suspected of assault that kills 6, wounds 30 on eve of cease-fire. NATO planes take off to retaliate but, unable to pinpoint targets, are called back.

Less than 48 hours before a U.S.-brokered cease-fire, suspected Bosnian Serb gunners launched deadly bomb attacks Sunday that killed or wounded dozens of civilians and sent NATO warplanes scrambling in pursuit, U.N. officials said.

At least six women and children were killed and 30 wounded when a cluster bomb slammed into a Muslim refugee camp at Zivinice in north-central Bosnia-Herzegovina, U.N. officials said. North Atlantic Treaty Organization aircraft that were summoned to respond failed to pinpoint their targets, and the strikes were called off because of bad weather.

Bosnian Prime Minister Haris Silajdzic threatened to call off peace talks, and the cease-fire scheduled to begin at 12:01 a.m. Tuesday suddenly seemed in danger.

“The Serbs are continuing to kill our people, and we have to bury our children again,” Silajdzic said. “If they continue the attacks, negotiations should be suspended.”

Bosnian state television showed pictures of sobbing mothers and bloodied children being evacuated from the refugee center near the government-held city of Tuzla, a U.N.-designated “safe area.” Most of the refugees came from the former safe areas of Zepa and Srebrenica, which fell to the Serbs in July.

Following the attack on the Zivinice camp, which U.N. officials said was the work of an M-87 Orkan rocket equipped with a cluster-bomb warhead, Bosnian television claimed that Serbian airplanes bombed a second northern town, Tesanjka, killing nine people, wounding more than 45 and overwhelming the local hospital.

The Croatian state news agency, HINA, reported that Serbian planes also dropped cluster bombs on villages in the Croat-held Usora River valley of northern Bosnia, with many civilian casualties.

NATO would confirm only two violations of the “no-fly” zone over Bosnia in the previous 36 hours.

Fighting raged in advance of the cease-fire, with all sides apparently hoping to seize the best possible position before battle lines are frozen.

Artillery and rocket duels were reported north and east of the town of Bosanska Krupa, near the Bihac enclave in northwestern Bosnia. And heavy fighting was reported to the southeast near Kljuc, a front-line town contested in recent days by Bosnian Serb and Bosnian government forces.

Bosnian Serb rebels warned that the presence of Croatian army troops in support of Bosnian government forces inside Bosnia constitutes “aggression” that poses a threat to the peace process.

The Bosnian government troops have made substantial gains against the Serbs, but only with the help of the Croatian army. Each time that the Croats have pulled back, the Serbs have been able to regain lost ground.

Bosnian Serb television, commenting on the attack at the refugee camp, accused the Muslim-led but secular Bosnian government of committing “a massacre against [its] own civilians.”

Tuzla’s air base, which houses a U.N. installation, also came under repeated mortar fire, as did a unit of Pakistani U.N. peacekeepers in nearby Banovici, but no significant damage or casualties were reported.

Troops from all warring factions Sunday cleared a valley peppered with mines to make way for electricity to be reconnected in Sarajevo, the Bosnian capital. U.N. officials said lights might be flicked on tonight but that it was not likely that gas will be flowing by the Tuesday cease-fire deadline.

The mines were planted by the war’s three factions near a hill in Kokoska, about 12 miles west of Sarajevo and site of the capital’s main power lines. The lines were damaged, and international engineers were set to string new cable once the mines were cleared.

Gas is more complicated because it originates in Russia. Moscow--a traditional Serbian ally now owed millions of dollars in unpaid energy bills by the Sarajevo government--must give the go-ahead for the gas to be turned on. That had not happened by Sunday night despite intense diplomatic lobbying, U.N. officials said.

The government has insisted on the full restoration of utilities, which had been severed by besieging Serbs, as a condition of the truce. For more than six months, Sarajevans have been reduced to cooking over firewood and spending their nights by candlelight because of the lack of electricity and gas. With winter coming, gas for heating is especially crucial.

Despite the crescendo of military activity, Western officials held out hope that the cease-fire will proceed nevertheless. They pointed to the general war fatigue that seems to have propelled the factions to accept U.S.-sponsored diplomacy.

“We are hopeful that the cease-fire will go ahead,” U.N. spokesman Jim Landale said. “We are hoping this [fighting] won’t jeopardize it.”

Bosnian Serb leader Radovan Karadzic said the cease-fire might hold because it was brokered by U.S. officials, who hold sway over both the Croats and Bosnian government forces.

And, contradicting Silajdzic, Bosnian President Alija Izetbegovic said utilities, not Sunday’s shelling, will determine whether the cease-fire happens.

“We gave conditions . . . [and] if the conditions are fulfilled, we will have a cease-fire, and if not, we won’t have a cease-fire until the conditions are fulfilled,” Izetbegovic said.

The cease-fire was brokered by Assistant Secretary of State Richard Holbrooke as one step in a long and arduous process aimed at ending 3 1/2 years of brutal bloodshed.

The settlement under negotiation would divide Bosnia between the Serbs and a Muslim-Croat federation.