In Sarajevo two children - a three-year-old girl and a seven-year-old boy - were killed yesterday afternoon by a Serb shell. In the north-west, the Bosnian Serbs launched an air raid on a hydro-electric power station in the Bihac pocket, which was undetected by Nato aircraft supposedly enforcing the "no-fly" zone. Nato aircraft have not been flying over Bosnia itself since the shooting down of a United States F-16 fighter on 2 June.
"It seems to be very heavy fighting," said Lieutenant-Col onel Gary Coward, the United Nations spokesman in Sarajevo. "Given the continuing skirmishes, the commando-style raids into and out of the enclave, it is a picture of a build-up of tension."
The Serb aircraft, a super Galeb, fired rockets at the power station. The Bosnian Serbs have few aircraft, but with Nato aircraft steering clear of Bosnia itself, they can now get airborne, attack targets and land again before Nato aircraft can intercept them.
Nato sources have made it clear, however, that in the event of a large- scale attack, Nato might respond by attacking Serb airfields.
As the fighting between Bosnian government troops and Serbs continued unabated, the role of the new, 10,000 strong UN rapid reaction force and the timing of its arrival remained confused.
The French Foreign Ministry said talks were under way with the Bosnian Serbs to try to get UN relief convoys through to Sarajevo over Mount Igman. A spokesman, Yves Doutriaux, said French UN peace-keepers on the mountain would fight back if attacked. The Serbs have continually fired on traffic using the snaking road, the only route into Sarajevo from the south.
But Mr Doutriaux joined UN spokesmen in softening a statement by the French armed forces chief, Admiral Jacques Lanxade, that the new Rapid Reaction Force would be used to prise open corridors and keep them open permanently. He also said the RRF would be active from the weekend, which other sources denied, although half of it - the multinational brigade, formed mainly from troops already in Bosnia - is in position.
The advance party of the other half of the RRF, the British 24th Airmobile Brigade is expected to fly to Split tomorrow, and to move into Ploce, further east down the Adriatic coast, where they will set up camp - possibly in tents or portable cabins, although negotiations continue with the Croatian authorities.
The remainder, about 4,000 troops, including a Battalion of the Royal Anglian Regiment and about 50 helicopters, will filter in over the following month. Another battalion, from the Light Infantry, will stay in Britain on seven days' notice.