KABUL: A civilian helicopter ferrying humanitarian aid was shot down in a southern Afghan province where fighting with the Taliban is raging, killing all six Ukrainian crew members and a child on the ground, officials said. Two U.S. Marines and an Italian soldier died in the latest clashes.

The transport helicopter crashed in flames Tuesday in the Sangin district of Helmand province, the center of Afghanistan's opium poppy cultivation where thousands of Marines are conducting their biggest offensive since the hardline Islamic movement was ousted from power in 2001.

NATO officials in Kabul said the cause of the crash was under investigation and gave no further details.

But the civil aviation authority of the former Soviet republic of Moldova said a rocket or a missile struck the Mi-26 helicopter, owned by the Moldovan air charter company Pecotox-Airi and carrying six Ukrainians. The helicopter was ferrying humanitarian aid when the crash took place, the Moldovans said in a statement.

The Taliban posted a statement on its Web site claiming the helicopter was brought down "by anti-aircraft fire" with 37 British soldiers on board. Moldovan and British authorities said no British troops were on the helicopter. Daud Ahmadi, the spokesman for the Helmand governor, said a 6-year-old child on the ground was also killed.

The crash occurred about a mile from a British base military base, according to Fazel Haq, a senior local official. The helicopter exploded in a ball of flames, generating smoke that could be seen over a wide area.

Last week, two Canadian soldiers and one British trooper were killed in a helicopter crash in Zabul province. Officials said that crash did not appear a result of hostile fire.

Afghanistan's harsh mountainous terrain, the lack of roads and the heavy use by the Taliban of roadside bombs have prompted international military forces to rely heavily on helicopters for transportation and supply missions. A shortage of military helicopters has forced some NATO nations to contract with private companies.

The two American Marines were killed Monday in a "hostile incident" in Helmand, according to U.S. military spokeswoman Capt. Elizabeth Mathias. She released no further details.

Those deaths brought to at least 107 the number of U.S. troops killed in Afghanistan so far this year, compared with 151 in all of 2008. As of Monday, at least 660 members of the U.S. military had died in Afghanistan, Pakistan and Uzbekistan since the war began in 2001, according to the Defense Department. Of those, the military says 492 were killed by hostile action.

One Italian soldier was killed and three were wounded Tuesday when a roadside bomb struck their convoy about 30 miles north of the city of Farah in western Afghanistan, the Italian Defense Ministry announced. Italy has about 2,800 soldiers in Afghanistan, mostly in Kabul and the west of the country.

U.S. commanders are trying to turn the tide of the Taliban-led insurgency, which has transformed much of southern and eastern Afghanistan into no-go zones for Afghan authorities.

President Barack Obama has ordered 21,000 additional U.S. troops to Afghanistan this year. There are about 57,000 U.S. troops currently in the country, and the number is expected to rise to at least 68,000 by the end of 2009.

Obama said Tuesday that he hopes military operations in Afghanistan can transition to a different phase after the Afghan presidential election set for Aug. 20. Obama said he is looking for an exit strategy in which the Afghan army, police, courts and government take more responsibility for the country's security.

To that end, about 4,000 U.S. Marines launched their operation July 2 in Helmand province, hoping to prevent Taliban fighters from disrupting the presidential ballot in what has been a longtime Taliban stronghold.

British forces, meanwhile, are facing a tough fight in another area of Helmand. Britain's 9,000-strong force has lost a record 15 soldiers this month — including eight in a 24-hour period, prompting a national debate over whether the conflict is still winnable.

The British Ministry of Defense announced Tuesday it was sending another 140 soldiers to Afghanistan from a British base in Cyprus to bolster the war effort.