Bosnian Serbs tightened their stranglehold on the U.N. peacekeeping force today, taking at least 41 more soldiers hostage as the U.N. command awaited guidance from Western leaders on how to respond to the deepening crisis.

In the midst of the hostage standoff, Bosnia's foreign minister was killed, along with three other officials, when his helicopter was shot down over Croatian Serb territory, apparently by a Serb missile. Irfan Ljubljankic was the most senior Bosnian government official to be killed in the three-year-old communal war. He had been visiting the besieged town of Bihac.

Since NATO airstrikes Thursday and Friday aimed at ending Serb shelling of Sarajevo, the Bosnian capital, the Serbs have taken 211 U.N. soldiers prisoner -- holding many of them as human shields. They have surrounded 156 more in small groups at observation posts and heavy weapons collection points.

Serb units also took control of the last remaining U.N. weapons collection points in their territory and the guns stored there. The move effectively ended the mechanism of a heavy-weapons exclusion zone, established by NATO, that had brought 15 months of relative peace to Sarajevo.

The peacekeepers taken today included 33 British and eight Canadian troops. The British were kidnapped at gunpoint around 2 p.m. local time by Serb militiamen who attacked their observation posts north and east of the Gorazde "safe area" in eastern Bosnia.

About as many U.N. troops managed to elude capture, many under fire. In one instance, several U.N. soldiers drove an armored personnel carrier through a Serb barricade. The British U.N. commander in Gorazde began withdrawing troops from the most vulnerable observation posts after the incident. The Serbs went after the British peacekeeping troops for political reasons, a U.N. official said. "In their eyes, they added more aces up their sleeve to have some Brits," he said. "It puts more pressure on the main two capitals -- Paris and London." Britain has the second-largest contingent in Bosnia, after France, and generals from the two countries hold the three most important posts in the U.N. force in the region.

The Serb military commander, Gen. Ratko Mladic, threatened British peacekeepers if four Serb militiamen captured by French troops in fierce combat Saturday in Sarajevo were not released by 6 p.m. local time tonight, a deadline that expired without known action.

U.N. officers are worried about the use of the considerable military equipment the Serbs have captured in the past three days. In addition to the weapons, flak jackets and helmets of 211 peacekeepers being held prisoner, they have six French light tanks and 11 Ukrainian and French armored personnel carriers.

"Our worry is the use of our equipment by Serb soldiers to attack our troops or Bosnian troops," said French Maj. Guy Vinet, a U.N. spokesman.

Alliance warplanes made brief appearances in the skies over Sarajevo, but have carried out no further raids. Serb fighters apparently fired outdated antiaircraft guns at the planes today, but NATO said the pilots did not report coming under fire.

The Serbs have capitalized on the international community's indecision and have forced a shift in the debate in Western capitals from how best to preserve the mission in Bosnia to how to protect the lives of their troops.

"What they are doing now will be very successful in the short term," said a senior U.N. official in Zagreb. Unless the United Nations responds with force, the Serbs will be able to dictate the future terms of the peacekeeping mission to their liking, he said.

"But they will pay a very high price politically in the long run," the official said. "They will never be accepted as a credible entity in the international community, which is their ultimate goal."

For the moment, however, U.N. officials in Bosnia face a crisis that has sharpened daily in the past five days.

"We hope that the decision will be made sooner rather than later," a U.N. official said. "We don't like being left in the darkness without any clear guidelines on how to proceed."

In Washington, President Clinton's senior foreign policy advisers, including Secretary of State Warren Christopher and Defense Secretary William J. Perry, held a two-hour discussion at the White House of a French proposal for reorganizing the U.N. peacekeeping mission.

A U.S. official said the participants agreed that "the air strike option" should be left open but that lessons should be drawn from the reaction of the Bosnian Serbs, including the need for "more careful strategic planning" to avoid the taking of hostages en masse.

The advisers reviewed contingency plans that could involve the use of U.S. Marines and other commando units to rescue U.N. peacekeepers who are surrounded by Bosnian Serbs. The United States has promised to help in any emergency withdrawal of peacekeepers from allied nations, and could send up to 25,000 troops to assist in any general withdrawal.

{On Saturday, the United States moved a three-ship task force carrying a 2,000-Marine Rapid Deployment Force into the Adriatic as a contingency should a withdrawal of U.N. peacekeeping forces be ordered, Washington Post staff writer Dana Priest reported. {The amphibious ships -- the USS Kearsarge, USS Pensacola and USS Nashville -- were taking part in routine exercises off Sardinia when Adm. Leighton W. Smith Jr., commander of U.S. naval forces in Europe, decided to send them closer to the fighting in Bosnia. Smith, who also is NATO commander of the Bosnian operation, moved the ships "as a prudent measure" but there are no plans to order troops ashore, a Pentagon source said.

{The three ships join an aircraft carrier and an Aegis destroyer that also have been moved to the Adriatic, the source said.}

The French aircraft carrier Foch left the Mediterranean port of Toulon to bolster France's forces in the Adriatic. In London, the Ministry of Defense said it would send 1,200 soldiers to Bosnia "as soon as possible" and ordered another brigade of 5,000 soldiers to prepare for deployment, the Associated Press reported.

Christopher will fly to The Hague for a meeting Monday of the contact group of major powers -- the United States, Russia, France, Germany and Britain.

Across Europe, Western leaders held crisis meetings, but no decisions were expected at least until NATO foreign ministers meet Tuesday, also in the Netherlands. The British government, after an emergency cabinet meeting, said it will send two artillery batteries and an armored engineer squadron to Bosnia as soon as possible. In a statement, it threatened severe consequences if the peacekeepers are not released unharmed.

This morning, Serb troops shelled the northeastern town of Tuzla, killing one man. One of the shells fell in the square where 71 residents were killed Thursday.

The hostages and the Serb threats against peacekeepers remain the United Nations' top concerns. Serb authorities appear to be dispersing the hostages over a wide area.

Ukrainian peacekeepers captured Saturday were seen being put on buses heading north from Sarajevo. At least 17 U.N. officers spent another day chained to potential NATO targets.

A U.N. officer said today that a plan for two groups of French troops to fight their way to freedom with the aid of NATO close air support was scrapped Saturday when the Serbs moved in reinforcements. Those troops remain locked in a tense standoff with more than 100 Serb militiamen and at least four tanks.

The United Nations complained strongly about the treatment of its personnel in Serb hands.

"The Bosnian Serb army, commanded by General Mladic, continues to behave like a terrorist organization, chaining unarmed peacekeepers to potential military targets as human shields, threatening U.N. positions with force, holding guns to U.N. officers' heads threatening to kill them," Alexander Ivanko, a U.N. spokesman, said.

He suggested that such acts would be brought to the attention of the U.N. War Crimes Tribunal meeting in The Hague.

In Paris, French Prime Minister Alain Juppe criticized the ultimatum issued by the U.N. commander in Bosnia Wednesday that precipitated the crisis. Intended to end intensified shelling of Sarajevo and restore respect for the crumbling U.N. operation, the threat led to NATO raids against a Serb ammunition dump and prompted the hostage-taking.

"Ultimatums and air strikes must be used after reflection and preparation," Juppe said on French television. {Maj. William Taylor, a U.N. spokesman, said the Bosnian foreign minister's helicopter came down in territory held by Croatian Serbs, just west of the Bosnian-Croatian border, the Associated Press reported.

{Croatian Serb forces said they downed the helicopter, the Croatian Serb news agency ISKRA reported.} Staff writer Michael Dobbs in Washington contributed to this report. CAPTION: A masked Bosnian Serb guards a captured Brazilian U.N. soldier, Maj. Harley Fihno, handcuffed to a Serb-held facility on Mount Jahorina, near Sarajevo. CAPTION:Civilians in Tuzla take cover during new shelling by Bosnian Serbs at the site of a barrage Thursday that killed 71 people. One person was killed yesterday. CAPTION: Bosnian Serbs guard captured U.N. equipment at Lukavica base near Sarajevo. Serbs have seized arms and vehicles. CAPTION: Irfan Luibljankic