Sarajevo resounded to the thunder of artillery, tank and mortar fire in the second day of a battle for three Bosnian bunkers on a rocky hill overlooking an important Serb supply road. The airport, which sits on the front line, went on to red alert as fighting broke out south-west of the runway.
One Russian peace-keeper was wounded and a French soldier was injured by shrapnel. At least 11 people in the city were hurt.
Two United Nations flags fluttered in the breeze at either end of the old Jewish cemetery, obscured by clouds of smoke and dust from front- line houses hit by shelling.
Flashes of light on the steep slopes of Debelo Brdo, a hill above the cemetery, and plumes of smoke, marked the impacts of shells on trenches on the edge of no man's land.
UN officials shuttled between government and Bosnian Serb military commanders seeking a cease-fire, but their results were "inconclusive", a spokesman said.
For the second day, the Bosnian Serbs attacked three government-held bunkers in no man's land, but neither side managed to push the other back, the UN said.
The city streets were deserted, as people obeyed government orders to stay at home unless it was vital. The UN withdrew anti-sniping teams from Sniper Alley for safety reasons. Yasushi Akashi, the UN envoy, urged the warring parties "not to squander what chances remain for peaceful dialogue".
But the Bosnian government has lost faith in the international peace plan it signed last year, since the five-nation Contact Group's efforts to cajole the Serbs to sign up have come to naught. In the north-west enclave of Bihac, the government Fifth Corps has pushed south, taking the Serb-held town of Ripac yesterday, according to the UN. The Serbs retaliated by shelling the UN-declared "safe area" of Bihac, killing three people.
The past two days bode ill for the UN mission, which the Secretary-General, Boutros Boutros-Ghali, wants to scale down. The peace-keepers have been unable to enforce the heavy-weapons exclusion zone around Sarajevo, to deter attacks on the "safe areas"; or funnel enough aid to the capital and the enclaves. The UN for six weeks has been able to use Sarajevo airport only to supply its own troops. In the past, the airlift accounted for 75 per cent of the aid reaching the city.
The Bosnian ambassador to the UN, Muhammed Sacirbey, complained: "This is another way to take something away from the Bosnian people without giving us the right to defend ourselves."
Sarajevo is still under an arms embargo, although illegal weapons purchases have gone some way to closing the enormous gap with the heavily armed Serbs.
"It's not a bully ganging up on a child any more," said one UN official in Sarajevo. "But that was the situation when the resolutions [permitting Nato air strikes in defence of the safe areas] were passed."
In practice, the peace-keepers have been reluctant to call in air strikes, for fear of escalating the situation, most recently last week, when a Serb shell killed 11 Bosnians.