UNITED NATIONS -- The U.S. ambassador to the UN on Thursday displayed intelligence photographs that she said may depict mass graves near the Bosnian town of Srebrenica containing as many as 2,700 bodies.


Ambassador Madeleine Albright told the Security Council that the eight photographs, along with witness accounts, provide "compelling evidence ... that the Bosnian Serbs executed civilians outside Srebrenica,'' her spokesman, James Rubin, said.


One photograph showed a large field surrounded by trees. A U.S. official, speaking on condition of anonymity, said the spot, near the "safe area'' of Srebrenica in eastern Bosnia, may have been used to hold prisoners.


A second photograph showed a tree-lined area about a kilometer from the field where large patches of earth had been disturbed. Tracks from heavy vehicles led to the patches.


The patches in the photo are believed to be mass graves containing up to 600 bodies, the U.S. official said. Mass graves in the area likely contain 2,200 to 2,700 bodies, the official said.


General Ratko Mladic, the Bosnian Serb military leader, visited the area shortly after his forces took the Bosnian town, and promised the refugees safety, the U.S. official said. But a witness, a 63-year-old Bosnian, later told U.S. investigators that refugees were lined up in groups of 20 to 25 and gunned down.


The witness survived by hiding among the dead, the official said.


Some 6,000 men and boys remain unaccounted for after the Bosnian Serb capture last month of the UN-declared "safe areas'' of Srebrenica and Zepa.


Albright addressed the council as it considered a draft resolution warning that "those who commit violations of international humanitarian law will be held individually responsible."


The draft also demands that Bosnian Serbs give international human rights organizations immediate access to refugees from Srebrenica and Zepa.


As the United Nations considered the aftermath of Serb advances in Bosnia, Serb refugees of the latest Croat offensive in Krajina streamed into Serbia on Thursday, after running a gauntlet in which angry Croat mobs attacked their cars with bricks and rocks.


Many in the first wave of Serbs to reach Dobanovci, west of Belgrade, were men, whose wives and children had either left earlier or stayed behind. Many were soldiers, who were later seen being put into Yugoslav army trucks, presumably to be sent back to the front lines.


Back in Croatia, between 8,000 and 12,000 people, including wounded, were still stuck in Topusko without water, said UN spokesman Chris Gunness. Another 10,000 refugees were in the Dvor area. An additional 900 were in Knin, which fell Saturday.


An estimated 50,000 Serb refugees from Knin and other parts of Serb-held Croatia that fell early on were in northern Serb-held Bosnia, mostly in the Banja Luka area. Tens of thousands had passed through the area earlier, and estimates of the final refugee exodus from Croatia were as high as 200,000.