The Serbs said women and children were among the victims. "Many people and cars were on the bridge, so there is a great number of injured as well," they said.
Fifteen boats with rescue teams were searching for victims in the Velika Morava river at the town of Varvarin, the Yugoslav news agency said.
Nato refused initially to be drawn on whether the attack at Varvarin was another disastrous error. The alliance earlier admitted mistaken attacks on a refugee column in Kosovo and the rocketing of a train in southern Serbia.
The Nato spokesman Jamie Shea, said in Brussels: "A bridge is an important military target because they are responsible for reinforcement and resupply in Kosovo". If the blunder is confirmed, international pressure will increase on Nato to stop the attacks at least while diplomatic negotiations appear to yield results.
Serbia's state media said President Slobodan Milosevic was ready to accede to most of the conditions for a peace deal drawn up by the G8 group of Western powers plus Russia. The Russian Balkan envoy Viktor Chernomyrdin had met the Yugoslav president on his weekend visit to Belgrade.
Nato sources in Macedonia have privately admitted to growing confusion over preparations for a land offensive in Kosovo. Weeks after politicians began to prepare Western public opinion for a massive land invasion of Kosovo, Nato forces in Macedonia are as far as ever from being able to mount an assault, defence sources say. Announcements of massive reinforcements are misleading because all troops now being sent to the border countries will be needed to escort the refugees into the province in a "semi-permissive environment".
Sources say an operation to take Kosovo by force would need thousands more troops and much more equipment. Military strategists say politicians have delayed authorising the extra forces needed for combat for so long that a campaign before the harsh Balkan winter sets is already almost impossible. The terrain in Kosovo would have to be secured by the end of August at the latest, if more than 800,000 refugees now in Albania and Macedonia are to begin returning home this year.
To delay an invasion any later, they say, will hand a crucial strategic advantage to Mr Milosevic, because the return of bad weather will hinder air strikes, block land routes for the invading force and cover the thousands of mines the Serbs have laid with snow and ice. Senior officers from several Nato countries are exasperated at what they see as procrastination by politicians. They say they are receiving conflicting messages about the land war.
The British government is largely absolved from their criticism, because it pressed hardest for the alliance to prepare for a ground war to take Kosovo. With what is seen as a lack of firm leadership over the war in many capitals, especially Washington, the military commanders are trying to circumnavigate the control of civil servants and politicians. When the Pentagon forbade Nato to use Apache helicopters because of their vulnerability to anti-aircraft fire, Nato's commander General Wesley Clark has started using older Spectre gunships for similar missions.
The reinforcements being sent so fare are engineers and support groups needed to re- establish the basic infrastructure inside Kosovo when the refugees return. A strike force requires specialist troops, massive heavy armour, and airborne forces.Reuse content