BAGHDAD, July 1 (Reuters) - The number of civilians killed in Iraq fell sharply in June to the lowest monthly total since a U.S.-backed security clampdown was launched in February, Iraqi government figures showed on Sunday.The data, obtained from the ministries of interior, defence and health, showed 1,227 civilians died violently in June, a 36-percent fall from May and the lowest level in five months.
U.S. military officials said it was premature to draw conclusions about the effects of the crackdown, which is seen as a last ditch effort to avert full-scale sectarian civil war between majority Shi'ites and minority Sunni Arabs.
"We continue to be cautiously optimistic, (but) we are still very early in this process," said U.S. military spokesman Lieutenant-Colonel Christopher Garver.
U.S. President George W. Bush is under growing pressure from opposition Democrats and senior figures in his own Republican Party to show his war strategy is working after ordering 28,000 more soldiers to Iraq.
There are now 157,000 U.S. troops in the country.
U.S. public opinion has grown increasingly hostile to the war and June was a costly month for U.S. forces, with 101 soldiers killed. That made the April-June quarter the bloodiest since the U.S.-led invasion in 2003.
While U.S. military officials say the number of attacks across Iraq has remained steady in recent months, there has been a reduction in the past few weeks in the amount of big car bombings that often cause a heavy loss of life.
"Although the number of car bombs ... has remained relatively constant since almost November, the effects of those has come down significantly," Major-General Joseph Fil, commander of U.S. forces in Baghdad, said during a live link-up with Pentagon reporters on Friday.
One of the key aims of the crackdown is to dismantle car bomb networks operated by Sunni Islamist al Qaeda in and around Baghdad and to protect vulnerable places such as outdoor markets with high concrete walls to keep bombers out.
U.S. officials accuse al Qaeda of trying to tip Iraq into all-out sectarian civil war by attacking Shi'ites targets.
A car bomb attack at a Shi'ite mosque in central Baghdad on June 19 killed 87 people, the deadliest attack in the capital since 140 people perished in a Baghdad market bomb in April.
The number of bodies found daily around Baghdad, a barometer of the activities of sectarian death squads, has also shown a decline during the crackdown.
Police said they had found 16 bodies on Saturday in the capital, compared with 40 or 50 daily last year. However, on many days the average has been about 20 to 30 bodies found.
The Iraqi data showed 222 Iraqi police and soldiers were also killed in June, slightly higher than the previous month. It also showed that 416 insurgents and militants were killed in June and 2,262 were detained.
Fil said almost half of Baghdad's 474 neighbourhoods were under effective control after having been cleared of militants.
The core of U.S. strategy is "clear, hold and build" -- flushing militants from their strongholds, preventing them from returning with stepped-up security, and winning the trust and support of locals by improving basic services.