The attack on the north-eastern corner of the pocket, which fell last month to Bosnian government troops, is the most direct challenge to Nato and the UN in Bosnia since last April.
Rebel Serbs from the Krajina region of Croatia joined forces with their Bosnian brothers for the first time to attack Bihac from the north and east, using tanks, artillery and up to 1,000 troops, the UN said.
'This is considered to be a very severe increase in the tension and the fighting,' said Paul Risley, a UN spokesman in Zagreb. But by last night, the area was calmer. 'There has been heavy fighting but it has stopped,' said Commander Eric Chaperon, a UN spokesman in Sarajevo, after talking to French peace-keepers.
He said the offensive did not appear to have broken through Bosnian government lines. 'The front line seems stable; neither the Bosnian Serbs nor the Krajina Serbs have advanced a lot,' Commander Chaperon said.
But the UN was angered by the attack on British Nato jets overflying the area. Two Royal Navy Sea Harriers, which were on a routine training mission over Bihac, were forced to take evasive action yesterday afternoon when the pilots spotted a SAM-7 missile. The jets, which were flying within range of the heat-seeking missile, dropped flares and returned safely to HMS Invincible in the Adriatic. An official said the UN 'believed' Bosnian Serbs fired the missile. 'This is a direct firing at a Nato aircraft,' said Mr Risley. 'That is a very serious issue for Unprofor (UN Protection Force) and Nato.'
Nato launched air strikes on Serbian forces last April when they attacked the eastern Bosnian Muslim enclave of Gorazde. The Serbian attack raises problems for Western countries and Russia, which are seeking ways to reward President Slobodan Milosevic of Serbia for his decision to abandon the Bosnian Serb leadership.
The UN was last night 'reviewing its options', one of which might include retaliatory air attacks. It is allowed to call in close air support if troops come under fire, and to request Nato air strikes if a Bosnian 'safe area' comes under attack. Bihac town has this status, but it does not seem to apply to the whole pocket.
Yesterday's action was the first undertaken jointly by Serbs from Croatia and Bosnia and as such is a worrying development. The Bihac pocket, an untidy corner of rolling green hills, woods and meadows, is bounded to the north and west by Serb-held Croatia, and to the south and east by hostile Bosnian Serbs. The northern part of the enclave was held, until last month, by Fikret Abdic, a renegade Muslim businessman who signed a peace deal with the Bosnian Serbs and went to war with the Bosnian armed forces.
The Pope, who called off a 'pilgrimage of peace' to Sarajevo this week for security reasons, broadcast an appeal from his summer home in Italy calling for an end to ethnic and religious barbarism in Bosnia, Reuter reports.
Some 800 people filled Sarajevo's Catholic cathedral and others sat by radio and television sets to hear the Pope say a special Mass for Bosnia. Speaking in Serbo- Croat, he delivered the sermon he had intended to preach at an open- air service in the city.Reuse content