BAGHDAD (Reuters) - A suicide bomber killed as many as 33 people in an attack on tribal leaders and security officials in western Baghdad on Tuesday, officials said.

Security spokesman Major-General Qassim Moussawi said the bombing, the second big attack in the Iraqi capital in three days, killed 28 people and wounded 28 others as dignitaries toured a crowded market in the Abu Ghraib district.

Other official sources put the death toll as high as 33 killed and 52 wounded, saying that security officials, civilians, women and schoolchildren were killed. A senior Abu Ghraib's army officers was among the dead.

Abu Ghraib mayor Shakir Fiza said a senior Interior Ministry official was headed toward a tribal reconciliation conference in Abu Ghraib's municipal headquarters when he got out of his car and began talking to people at the market.

Then the bomber approached and blew himself up, he said.

Al-Baghdadiya, an independent television station, said two of its journalists were killed in the attack. A journalist at Al- Iraqiya state television said four colleagues were wounded.

While violence has dropped sharply in Iraq since the height of the sectarian and insurgent bloodshed unleashed by the U.S.-led invasion in 2003, insurgents still stage regular attacks, especially in the volatile northern city of Mosul.

On Tuesday, a car bomb killed two civilians and wounded six people in al-Hamdaniya, just east of Mosul.

The improvement in security has been particularly effective in Baghdad, where Iraqis are cautiously resuming a more normal life. Yet violence continues to strike there too. On Sunday, a suicide bomber killed 28 people at the main police academy.

We expect these things to happen from time to time, especially when there are political openings bringing together different parties, said security spokesman Tahseen al-Sheikhli, blaming pockets of Sunni Islamist al Qaeda or militants loyal to Saddam Hussein's banned Baath party for such attacks.

RECONCILIATION ELUSIVE

Political analyst Hazim al-Nuaimi said that officials should not be so quick to blame al Qaeda.

These attacks raise questions about political power struggles, he said.

The latest attack took place days after the United States said it would reduce its troop force of around 140,000 before a full withdrawal date by the end of 2011, raising questions about whether local forces will be ready to prevent Iraq sliding back into large-scale bloodshed.

Reconciliation among rival political factions is proving even more difficult than combating insurgents. Many factions remain mutually suspicious and hostile after six years of sectarian killing between Iraq's Sunni Arab minority, dominant under Saddam Hussein, and its Shi'ite Arab majority.

Prime Minister Nuri al-Maliki, a Shi'ite whose political fortunes were strengthened following recent local polls, has stepped up calls for reconciliation in the past few days.

But many opponents see such calls as mere rhetoric and accuse Maliki's government of blocking steps to reincorporate thousands of former Baath party members, who were fired by U.S. authorities in 2003, back into the government.

As the government seeks to tout its security gains, it has made a habit of inviting journalists to accompany officials to tour markets, view weapons caches and more.

(Writing by Missy Ryan; Editing by Angus MacSwan)

Iraq