BAGHDAD, Jan. 7 -- More than 17,000 Iraqi civilians and police officers died violently in the latter half of 2006, according to Iraqi Health Ministry statistics, a sharp increase that coincided with rising sectarian strife since the February bombing of a landmark Shiite shrine.

In the first six months of last year, 5,640 Iraqi civilians and police officers were killed, but that number more than tripled to 17,310 in the latter half of the year, according to data provided by a Health Ministry official with direct knowledge of the statistics. The official, who spoke on condition of anonymity because he was not authorized to release the information, said those numbers remained incomplete, suggesting the final tally of violent deaths could be higher.

Much of last year's politically motivated bloodshed unfolded in Baghdad. The Bush administration is considering sending more U.S. troops there, as the newly ascendant Democrats in Congress press for a military withdrawal. Bringing stability and rule of law to the capital is a cornerstone of the administration's strategy to exit Iraq. Iraqi Prime Minister Nouri al-Maliki announced over the weekend his own security push to tame Baghdad's sectarian strife.

Last year's spike in casualties occurred despite an ambitious U.S. military operation in the capital, Together Forward, that involved thousands of U.S. and Iraqi troops cordoning off some of the deadliest neighborhoods and conducting house-to-house searches.

"We have been in a reaction mode in many ways to the events that occurred because of the [February] bombing of the Golden Mosque in Samarra, and that began a cycle of sectarian violence that we've been working very, very, very hard to keep under control," Lt. Gen. Peter W. Chiarelli, the former second-ranking commander in Iraq, told reporters last month.

"Now, I'm not in any way happy with what I see in Baghdad. The level of violence is way too high," he added.

The Health Ministry's full-year death toll of 22,950, although incomplete, is higher than the 13,896 violent deaths of civilians, police officers and soldiers reported Jan. 1 by Iraq's ministries of defense, health and interior. The United Nations, in a November report, estimated that more than 28,000 Iraqi civilians had died violently in the first 10 months of 2006, but that count was disputed by the government. The differences in the numbers could not be reconciled.

Iraq's death toll from violence is controversial because it provides a vivid report card on the difficulty of U.S. and Iraqi efforts to bring order to the country. Neither the U.S. government nor the military provides death totals for Iraqis.

"It is often very difficult to gain consensus on the numbers of casualties in Iraq. It really is a government of Iraq issue," said Lt. Col. Christopher C. Garver, a U.S. military spokesman. U.S. and Iraqi officials have discouraged Baghdad's medical officials from releasing morgue counts.

The Iraqi government does not provide a single official death toll, leaving it up to individual ministries to release data, which are often conflicting.

The Health Ministry compiles data from morgues across the nation and from government hospitals. Those figures include Iraqis killed in bombings, terrorist acts, militia attacks, roadside explosions, drive-by shootings, kidnappings and other acts of violence. They also include the numerous unidentified corpses that turn up virtually every day, often handcuffed and showing signs of torture.

The Health Ministry data are believed to be more reliable than those issued by other sources because they are based solely on death certificates. But the Health Ministry, as a policy, does not publicly release these statistics. The ministry is under the control of the Shiite religious party of Moqtada al-Sadr, whose Mahdi Army militia is behind much of the sectarian killing.

The numbers are considered so sensitive that some Iraqi officials, when told of the Health Ministry data, dismissed them as exaggerated, but at the same time did not offer any other numbers. Previous reports about such body counts have drawn similar denials.

"I don't know of these numbers," said Health Ministry spokesman Qasim Yahya. "The Ministry of Health does not give out such numbers."

He referred all comments to the Interior Ministry, which he said was responsible for releasing such statistics.

Brig. Abdul-Karim Khalaf, an Interior Ministry spokesman, said the Health Ministry was "not authorized to give out such statistics. It's a very big number. It's not close to the truth."

The Interior Ministry's figures are based primarily on data from police stations, police units and emergency patrols. Those numbers do not include the wounded who die later from their injuries, those kidnapped and later killed, armed men who die in clashes with U.S. or Iraqi forces, unidentified bodies, and other categories of deaths.

Another source of data is the United Nations, which relies on reports it culls from the Health Ministry, the Baghdad morgue and government hospitals, and releases death figures every two months. The organization does not include Iraqi police or military casualties in its reports.

The United Nations reported 28,076 violent deaths of civilians in the first 10 months of 2006, including 3,709 killed in October, according to its latest report, issued in November. At that time, Iraqi government spokesman Ali Dabbagh disputed the U.N. numbers as "inaccurate and exaggerated" because they were not based on official government reports.

"Yes, we have casualties, but not that huge number of casualties," Health Minister Ali Hussein al-Shamari said on Iraqi television. "The true number might be a quarter that, although we feel sorry for those who are dying. But they want to mislead the world about the conditions in Iraq." During a visit to Vienna that month, however, he said as many as 150,000 Iraqi civilians had died since 2003 as a result of violence. Dabbagh, who is traveling outside of Iraq, was not available for comment on Friday.

Sadiq al-Rikabi, a political adviser to the prime minister, Nouri al-Maliki, disputed the figures, saying they probably included those who were killed in car accidents or day-to-day crimes.

The Health Ministry official made clear that the statistics counted only those who had died from political violence.

"Everyone can guess, but what is the real number? I'm not sure if anyone knows how many people are killed due to the violence and the terrorism," Rikabi said.

The Associated Press count for last year, assembled from its daily dispatches, is roughly 13,700 civilians, police and soldiers. But the news service has said that it believes its figures are substantially lower than the actual number of deaths because it lacked access to government data. Iraq Body Count, a British-based research group that reports on civilian deaths in Iraq, says the number is at most roughly 58,000 since the 2003 U.S.-led invasion.

The group relies on deaths reported by the news media, and suggests on its Web site that its totals are an underrepresentation because "many if not most civilian casualties will go unreported." Critics have accused the group of grossly underreporting Iraqi deaths.

A study on Iraqi mortality rates published in October by the Lancet medical journal estimated that more than 600,000 Iraqis had died from violence since the invasion. That number was extrapolated from population surveys rather than a compilation of actual deaths. The U.S. and Iraqi governments, as well as Iraq Body Count, dismissed the Lancet findings as inaccurate.

The United Nations is scheduled to release death tolls for November and December within the next two weeks, an official said. According to the Health Ministry figures obtained last week, November's death toll was 3,293, while December's fell to 2,748.

In November, four family members of Abu Taha al-Adhami, a computer engineer in Baghdad, were killed, he said, and one was kidnapped and remains missing. During the first half of last year, he lost no relatives, he said.

"The violence wasn't that obvious during the first half of last year," he said. "During the second half, the violence started to grow and grow and become more severe. It's all because of the political atmosphere."

A Washington Post special correspondent in Baghdad contributed to this report.

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