SARAJEVO -- Serb aircraft attacked the UN safe area of Bihac in northwest Bosnia on Friday, according to UN officials and Bosnian media reports, and a missile struck the Bosnian parliament building in Sarajevo -- despite UN warnings that such attacks would prompt NATO air strikes.


The United Nations confirmed that warplanes fired a missile in a raid on the Moslem-controlled town, but NATO -- whose AWACS planes monitor the area -- could not confirm the attack.


"NATO cannot confirm the reports at this time," a spokesman at NATO's southern command in Europe said.


"I am not denying the attack took place, but the data we have collected with radar from the air has not determined that the attack took place."


Bosnian media said the raid was carried out by two or three Serb jets which took off from Udbina in Croatia.


In Zagreb, the UN said its officials had found evidence that napalm and cluster bombs had been used in the raid. But UN spokesman Paul Risley said no casualties had been caused.


In Sarajevo, the Bosnian parliament building's glass facade disintegrated when a missile caused an explosion which badly injured one woman.


UN spokesmen said that Serb forces fired similar missiles on the Bosnian presidency building Thursday.


The attack was bound to anger the UN, which said Thursday's attack on the presidency was "an outrageous and deliberate assault on the leadership of this government which deserves only the strongest condemnation."


Fighting in Bihac and the sharply deteriorating security situation in Sarajevo prompted fears Bosnia could soon plunge back into intense violence.


France and Britain agreed Friday to warn the United States they would have to withdraw their troops from Bosnia if it took further steps to undermine a UN arms embargo, a French spokesman said.


Presidential spokesman Jean Musitelli said President Fran?ois Mitterrand and Prime Minister John Major agreed at a British-French summit on the dangers of last week's U.S. decision to stop enforcing the arms embargo on the Bosnian government.


Earlier Russia, France and Britain urged the United States to stick with allied peace efforts in Bosnia and expressed fears of a military flare-up.


Meeting for the first time since Washington rattled its allies by its decision on the UN embargo last week, foreign ministers from the three nations reaffirmed backing for a current peace plan and ruled out any military solution.


"We agreed to emphasize the absolute need to maintain unity in the contact group" after the U.S. pullout, French Foreign Minister Alain Juppe said. The three renewed calls for a ministerial meeting of the contact group -- the United States, Russia, Germany, France and Britain -- in coming days or weeks.


But in Washington, NATO Secretary General Willy Claes played down any split between the United States and its European allies within the framework of the alliance.


"There are other things than the arms embargo in Bosnia," Claes told the annual meeting of the North Atlantic Assembly, which is the interparliamentary arm of NATO.


He said he was confident the United States and European allies would continue to cooperate on such challenges as nuclear weapons proliferation and efforts to avoid other regional conflicts in Europe, and on NATO policy in Bosnia except for the arms embargo.