(Adds Petraeus/Crocker statement, paragraphs 4-5)

By Paul Tait

BAGHDAD, Oct 1 (Reuters) - Civilian deaths from violence across Iraq fell 50 percent in September, in line with a drop in U.S. military casualties attributed to a boost in troop numbers, Iraqi government data showed on Monday.

Information from the health, interior and defence ministries registered 884 civilians killed in September, the lowest monthly total this year, down from 1,773 in August.

The casualties were also the lowest since Washington began pouring an extra 30,000 troops into Iraq as part of a security crackdown aimed at al Qaeda and other Sunni Arab militants and Shi'ite militias across the country.

"Although the extremists try to harm Iraqi citizens and their leaders, incite violence and derail the ongoing process of reconciliation, they are not succeeding," said the top U.S. commander in Iraq, General David Petraeus, and ambassador Ryan Crocker.

"Many of their foreign-born leaders are being killed and captured, and the levels of violence across the country, while still too high, are much lower than they were a year ago," they said in a joint statement.

A total of 850 civilians were wounded in September, the figures indicated, also well down on the previous month's 1,559.

The crackdown, which was launched in Baghdad in mid-February and then spread into other troubled areas, was designed to buy time for Iraq's leaders to reach political benchmarks aimed at reconciling majority Shi'ite and minority Sunni Arabs.

The drop in civilian violence came despite a warning by al Qaeda at the start of Ramadan, more than two weeks ago, that it would escalate attacks during the Muslim holy month and target tribal leaders who were cooperating with security forces.

The U.S. military said on Sunday that, while violence levels were still too high, attacks so far during Ramadan were down 38 percent on last year.

This was mainly because of the "surge" of extra troops and a change in strategy to move troops out of large bases into smaller combat outposts where they live and fight alongside Iraqis, military spokesman Rear Admiral Mark Fox said.

ONE-OFF ATTACKS

However, U.S. commanders have also voiced concerns that the Sunni Islamist al Qaeda may still be able to launch "spectacular" one-off attacks that cause mass casualties.

Coordinated suicide bombings aimed at the minority Yazidi community in northern Iraq killed 411 people on Aug. 14 -- over a quarter of all violent civilian deaths that month.

The previous lowest monthly death toll during the "surge" was in June -- the month when the U.S. troop buildup came into full effect -- when 1,227 Iraqis were killed.

The government figures showed that 78 members of the Iraqi security forces were killed, down slightly from 87 in August.

The figures also recorded the deaths of 366 militants, a drop of 106 from August, with the number of detentions also down by about a quarter despite the security crackdown.

The U.S. military death toll in September was the lowest since July 2006, with 63 killed, according to the Web site icasualties.org, which tracks military deaths in Iraq.

One U.S. soldier was killed by small arms fire during combat operations in eastern Baghdad on Sunday, the military said.

Washington has also focused on the success of a strategy of helping Sunni Arab tribal sheikhs in the westerly Anbar province to form local police units to drive al Qaeda from their areas.

Anbar was once the most violent province in Iraq for U.S. troops and Iraqis, but is now relatively safe. U.S. commanders have since worked on adopting similar models elsewhere in Iraq, although the strategy has yet to be tried in major urban areas.

U.S. President George W. Bush told Congress this month that successes in the unpopular war would allow for limited troop withdrawals of between 20,000-30,000 by July.

(Additional reporting by David Clarke in Baghdad)

AlertNet news is provided by