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6 Marines die in Afghanistan helicopter crash

Six United States Marines were killed when their helicopter went down in Southern Afghanistan. An investigation is under way, but U.S. military officials say there was no evidence of enemy activity in the area. NBC's Jim Miklaszewski reports.

Updated at 3:33 a.m. ET: A helicopter crash in Helmand province in southern Afghanistan killed six U.S. Marines, the NATO military command in Kabul told NBC News early Friday.

Officials said there were no signs of enemy activity in the area at time of the crash.

The Marines have a substantial presence in Helmand province.

"We are still in the process of gathering more information on the incident," an official told Reuters.

It is the worst crash since last August when 30 soldiers, including 22 elite Navy SEAL commandos, died when their helicopter came down in eastern Afghanistan.

The Helmand helicopter crash occurred on the same day seven civilians were killed outside a crowded gate at Kandahar Air Field, a sprawling base for U.S. and NATO operations, after a suicide attacker set off a vehicle laden with explosives. The Taliban claimed responsibility, saying they were targeting a NATO convoy.

On Wednesday, 13 civilians, including three Afghan policemen, were killed when a suicide attacker blew himself up in a bazaar in  Helmand province. At least 22 others were wounded in the blast in Kajaki district.

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NBC News, The Associated Press and Reuters contributed to this report.