U.S. Official Calls Tales of Serb Crimes ‘Credible’ : Balkans: After visiting Bosnia, assistant secretary of state repeats accounts of mass executions by rebels. He appeals for release of civilians.

The disabled man said he was one of 20 men blindfolded and lined up in a field. Shots rang out, he said, and bulldozers dug a mass grave.

A refugee said a shell landed near a group of fleeing civilians. It gave off a cloud that disoriented people, he said, and drove several to suicide.

Tales of Bosnia-Herzegovina, summer 1995.

Even as NATO officials on Tuesday scrambled to try to better protect U.N.-designated “safe areas” in Bosnia, the American government’s senior human rights official said he had heard “credible eyewitness accounts of mass executions” by Bosnian Serb soldiers and testimony of apparent chemical attacks on columns of Bosnian Muslim refugees.

Returning from a visit to Bosnia, Assistant Secretary of State John H. Shattuck expressed grave fears about the fate of more than 10,000 people still missing after the Bosnian Serb capture of the Bosnian Muslim enclaves of Srebrenica and Zepa.

“It is impossible to estimate how many may have been killed, but clearly that number is very substantial,” he said. “The accounts indicate that there is substantial new evidence of genocide and crimes against humanity in eastern Bosnia.” He appealed to the Bosnian Serbs for the release of civilian prisoners and access to prisoners of war.

Shattuck spent two days in the Bosnian cities of Tuzla and Zenica, where refugees have resettled. He said he spoke individually with about a dozen of them, as well as with local leaders and officials of the United Nations, the International Committee of the Red Cross and the Bosnian government.

The findings of the American inquiry parallel those of international agencies that have been systematically interviewing refugees; the U.S. report goes beyond others in its graphic accounts of executions and the possible use of chemical weapons.

Returning from the field, Shattuck passed through Zagreb, the Croatian capital, on Tuesday at a moment of extreme tension for Croatia, which borders Bosnia. Diplomats scrambled for emergency brakes, but there seemed almost a resignation to imminent war between Croatia and secessionist Croatian Serbs who occupy the Krajina region of the country.

U.N. Secretary General Boutros Boutros-Ghali sounded an alarm Tuesday, saying that “reports reaching me indicate that war . . . is imminent” between the groups. “I appeal most urgently to the parties to the conflict in Croatia to stop and reflect about the choice which now faces them,” he said in an appeal to Croatian President Franjo Tudjman and the leaders of the Krajina Serbs.

U.S. Ambassador Peter W. Galbraith visited Tudjman on Tuesday to urge restraint, and European countries also appealed for a negotiated settlement. U.N. officials said Croatia’s army was massed on high alert along the cease-fire line with Krajina, although nationalist Croats and nationalist Serbs did agree to meet for peace talks in Geneva later this week.

Galbraith told reporters that he had asked the State Department for a ranking American presence in the human rights investigation after fresh, detailed reports reached the embassy here last week of massive abuses following the fall of the safe areas.

Bosnian Serbs have refused international access to the captured enclaves except for cursory visits by the Red Cross to 200 or so detainees. There are persistent reports that captured Bosnian soldiers and civilians are being used by the Serbs as forced labor.

“I heard credible eyewitness accounts from refugees of mass executions of men and boys by Bosnian Serb soldiers,” Shattuck said. “According to several eyewitness accounts, many of those executed were buried in mass graves that were dug on the spot by bulldozers.”

The accounts evoked chilling echoes of Nazi executions half a century ago in World War II.

One disabled man, who Shattuck said was in his 50s, told of his detention with other Bosnian men in a warehouse. They were beaten, then individuals were led out, blindfolded and loaded onto trucks in groups of 20. They were driven to the killing ground and shot. The shots missed him, the refugee said. But he fell with the others and lay still while more trucks brought more victims. Later, he limped to safety.

A second, similar account came from a teen-ager grazed by the bullet meant to kill him, Shattuck said, adding: “I’ve also heard accounts of horrible brutalities committed against people who were trying to flee, including slitting of throats, cutting off of ears, noses, jaws and limbs of persons still alive. . . . I heard of the tying of persons to land mines, resulting in multiple killings.”

“There were many credible accounts of the shelling of large columns of civilians attempting to flee, and four separate accounts of the possible use of chemical weapons that severely disoriented fleeing people, causing several of them to commit suicide,” he said.

Almost all the refugees with whom he spoke, Shattuck said, told of the presence in Srebrenica and Zepa of Gen. Ratko Mladic, the Bosnian Serb military commander. “One eyewitness claimed he was present at a mass execution of men and boys,” he said.

Mladic and other Bosnian Serb leaders are already under indictment by an international war crimes tribunal of which the United States is a major supporter. If the new evidence is substantiated, Shattuck said, “it will and should lead to additional indictments of the Bosnian Serb civilian and military leadership . . . for the most serious crimes known to mankind.”

On Tuesday, North Atlantic Treaty Organization officials in Brussels agreed to extend the same protection promised to the haven of Gorazde--the threat of broad, sustained alliance air strikes if the Bosnian Serbs attempt an attack--to cover the other three remaining safe areas: Bihac, Tuzla and Sarajevo, the Bosnian capital.

The action was approved after a 3 1/2-hour meeting of the 16-nation organization’s policy-setting North Atlantic Council, with Britain and France supporting the American push to expand the threat to cover the other areas.

The ground rules to protect the other areas will be the same as those devised for Gorazde--meaning air strikes could be ordered directly by the commander of U.N. peacekeeping troops in Bosnia without the approval of the United Nations’ civilian leadership.

Meanwhile, the New York Times carried a report Tuesday, denounced by the Bosnian government, that quoted French U.N. peacekeepers as asserting that they had traced some deadly sniper fire in Sarajevo to a building occupied by Bosnian government forces.

Sniper attacks, which are usually blamed on Bosnian Serbs, have been assailed by human rights groups, which note that most casualties tend to be civilians. The Times said the French troops, on order of their commander in Sarajevo, had not further pursued, with either the United Nations or the Bosnian government, the purported discovery of sniper activity by Bosnian forces. The government said it made no sense for its forces to assault the very people they are seeking to defend.

Times staff writers Stanley Meisler and Art Pine in Washington contributed to this report.