Baghdad, Iraq ? More than 1,500 people died violently in Baghdad last month – nearly the same number as in July – and not the dramatic drop estimated just last week, when U.S. and Iraqi officials announced that their new security crackdown was working.

The Iraqi Health Ministry says its final August tally of violent deaths in Baghdad was 1,536. That is nearly three times the same agency’s preliminary estimate last week and shows a nearly undiminished epidemic of killings by insurgents and sectarian death squads.

When asked Thursday about the new, higher figures from the ministry, U.S. spokesman Lt. Col. Barry Johnson declined to provide an explanation or revised outlook. He referred The Associated Press to a statement on a U.S. military Web site that said the murder rate in Baghdad dropped 52 percent in August from the daily rate for July.

“The violence Baghdad endured in July receded during the month of August,” the statement by Maj. Gen. William B. Caldwell added. “Attacks in Baghdad were well below the monthly average for July.”

The Health Ministry offered no explanation for how the original estimate of 550 violent deaths in August could have been revised upward so dramatically.

The final figures for Baghdad, based on reports from morgues and hospitals, showed that 1,536 people died in Baghdad in August due to sectarian and political violence, said Deputy Health Minister Hakem al-Zamly.

The revised tally could be due in part to a surge in killings at the end of the month. More than 250 people died in bombings and shootings in Baghdad during the final week of August.

Delays in gathering information also could have played a role. The Health Ministry bases its monthly counts on reports from government hospitals and morgues, many of which are understaffed and lack computers.

Either way, the new numbers raise serious questions about the success of the security operation. U.S. and Iraqi officials have been eager to show progress in restoring security in Baghdad at a time when the country appears on the verge of civil war and support for the war is declining in the United States.

The confusion about the numbers underscores the difficulty of obtaining accurate death tolls in Iraq, which lacks the data reporting and tracking systems of most modern nations. When top Iraqi political officials cite death numbers, they often refuse to say where the numbers came from.

The Health Ministry, which tallies civilian deaths, relies on reports from government hospitals and morgues. The Interior Ministry, which command Iraqi’s police, compiles figures from police stations, while the Defense Ministry reports deaths only among army soldiers and insurgents killed in combat.

The United Nations keeps its own count, based largely on reports from the Baghdad morgue and the Health Ministry. A U.N. official said it would be announcing August figures later.

“It is impossible to get accurate casualty figures due to the chaos of the fighting, the malfunctioning of institutions and the politicization of the numbers,” said Fred Abrahams, a researcher at Human Rights Watch.

“In the end, we are left between estimates and guesstimations.”

The New York-based group tried to keep its own count, but gave up and now relies on comparing figures from multiple governmental and nongovernmental sources.