Muslim-led government forces expanded their strongest offensive of the 31-month war Saturday, trapping hundreds of Serb soldiers on a northwestern front and launching an attack on Serbs near Sarajevo.
The U.N. peacekeeping force, meanwhile, accused government forces of deliberately attacking French peacekeepers and threatened to call for NATO air strikes if the attacks were repeated. It was the most serious warning yet to the government army that it, too, could be hit by NATO air strikes. So far only the Bosnian Serbs have been targeted in the strikes.
The United Nations said four rounds from a government army artillery piece landed 25 to 50 yards away from a French peacekeeper observation post near the Javorak Valley, southwest of Sarajevo.
The Bosnian army, in a statement issued early today, denied that it had deliberately targeted the peacekeepers and said the fire was aimed at Bosnian Serb artillery positions.
The peacekeepers were trying to monitor a government infantry and artillery attack on Bosnian Serb positions just south of a demilitarized zone on Mount Igman, overlooking Sarajevo.
The United Nations said in a statement that it cannot allow either side to violate agreements such as the one establishing the demilitarized zone in August 1993.
"If U.N. observation posts or personnel are directly targeted by artillery or mortars, the U.N. will have no alternative but to request air support from NATO in self-defense," the statement said.
Col. Bertrand Labarsouque, a peacekeeper spokesman, said the shelling was considered a direct attack, but that U.N. officials decided not to request an air strike Saturday night.
In northwestern Bosnia, troops of the mostly Muslim government force surrounded the town of Bosanska Krupa, trapping several hundred Serb soldiers, U.N. officials said. Government army officials said their troops had entered part of the town.
With a prewar population of about 20,000 people, the town 130 miles northwest of Sarajevo would be the largest Serb-held town to fall to the government.
Serb leaders, stung beginning last week by their worst combat setbacks of the war, threatened retaliation with a major counterattack in the northwest or renewed bombardment of Sarajevo.
The government army reported that 18 Serb mortar rounds hit the government-held Sarajevo suburb of Hrasnica on Saturday, killing one civilian and wounding seven, including two children. The shelling followed almost day-long machine gun fire in the area.
An army official in Hrasnica said his troops were prepared to retaliate with a barrage on the Serb-held suburb of Ilidza if the shelling of Hrasnica continued.
Late Saturday, Bosnian Serb leader Radovan Karadzic ordered all soldiers to report to their units. The Bosnian Serb news agency SRNA said he also ordered civilians in the 70 percent of Bosnia controlled by Serbs to stay indoors.
SRNA later claimed that Serb forces had stopped the "fierce attack" by government troops on the northwest battlefront, but there was no immediate confirmation.
An estimated 10,000 Serbs have fled since government troops launched an offensive in the northwest Tuesday that has now captured 100 square miles of land.
The Bosnian army reported that several hamlets had been burned to the ground by retreating Serb soldiers. The United Nations could not confirm the burning or the government's claim of capturing a town called Kulen Vakuf. U.N. officials did report that hundreds of Serbs had fled the town.
Bosnia has been at war since April 1992 after the republic's minority Serbs rebelled at a vote by the Muslims and Croats to secede from Yugoslavia.