"We are expecting the death toll to reach around 50,000," a senior Interior Ministry official said, sharply raising the projected tally from the nearly 30,000 already buried.

Some hungry children may have died in the freezing nights tormenting tens of thousands forced to sleep in the open at Bam, putting a premium on blankets and clothing as well as medicines.

"If we consider that, on average, five people lived in each house we can say the death toll will reach 50,000," the Interior Ministry official said. Another official confirmed the forecast.

Such a figure could make the earthquake around the ancient Silk Road city the most lethal since a tremor at Tangshan in China that killed at least five times that many in 1976.

The death toll at Bam, 600 miles southeast of Tehran, may surpass that in northwestern Iran in 1990 and be double that of quakes in Armenia in 1988 and Gujarat in 2001.

Friday's tremor, which measured 6.3 on the Richter scale, struck just before dawn, killing entire families as they slept.

The Interior Ministry official said 80 percent of Bam's mud-brick buildings had been flattened and that many outlying villages had not yet been fully searched. Not only did bricks not leave the air pockets typical of modern concrete structures but their dust would have suffocated survivors, experts said.