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Kabul, Afghanistan (CNN) -- Nine U.S. service members in southern Afghanistan died in a helicopter crash in what is now the deadliest year for coalition and U.S. forces since the battle against the Taliban started nearly nine years ago.
The crash occurred in the Daychopan district of Zabul province, one of the several turbulent southern regions where coalition and Afghan troops have been battling the tenacious militant group for years.
"There are no reports of enemy fire at the time the air craft went down," NATO's International Security Assistance Force told CNN. ISAF is investigating the incident.
Two other service members, along with an Afghan National Army soldier and an American civilian, sustained injuries in the crash. They were taken to a NATO medical facility.
ISAF did not release the nationalities of Tuesday's crash victims, but a Western defense source, speaking on the condition of anonymity, revealed the nationalities of the nine.
A CNN tally brings the number of coalition troop fatalities this year to 526, a number that includes 350 Americans. These numbers surpass the previous highs -- 516 coalition troop deaths, including 313 Americans in 2009, and there are more than three months left in the year.
The ISAF force includes troops from more than 40 countries and its largest contingent is American.
Unpopularity with the long war in Afghanistan among Americans reached an all-time high in CNN polling in August, with 62 percent saying they oppose it. Moreover, confidence in the Afghan government is low. Seven in 10 Americans are not confident that Hamid Karzai's government can handle the situation there.
However, the United States is making a strong effort this year to fight the Taliban. U.S. President Barack Obama ordered the deployment of 30,000 extra U.S. forces to Afghanistan this year, increasing the total American troop commitment to almost 100,000, while at least 25 other countries pledged an additional 7,000 troops.
Defense Secretary Robert Gates recently said that now that the Iraq conflict is winding down, resources that were diverted to Iraq can be used in Afghanistan.
"Afghanistan became a second-tier priority for troops, equipment, and security and development assistance. Starting in 2003, the Taliban regrouped, refilled their ranks, re-constituted themselves in safe havens and re-entered Afghanistan. Violence began to increase significantly in 2005 and has grown worse ever since," he said.
"Today, for the first time in nine years, we now have the resources -- the troops and equipment, military and civilian -- needed for this fight," Gates said and the "full complement of surge forces" is only now being reached.
"The total international military commitment, when fully deployed, will reach approximately 150,000 -- more than three times the number when I became defense secretary going on four years ago -- including some 45,000 troops from our NATO allies and other partners. This dramatic increase in military capability is amplified by a tripling of deployed civilians and a substantial influx of trainers."
The Obama administration says it will begin withdrawing troops from Afghanistan in August 2011, depending on conditions on the ground.
CNN's Atia Abawi and Matiullah Mati contributed to this report.