A US Black Hawk helicopter crashed in southwestern Afghanistan on Thursday with four people believed to be on board, likely American soldiers, a US defense official told AFP.

"We're assuming they're American," said the official, adding he could not confirm whether those on board had been killed or wounded in the incident.

The official added that poor weather had likely been a factor, but cautioned that nothing was being ruled out.

"The crash site is secured; the cause is under investigation. Additional information will be released as appropriate," NATO's International Security Assistance Force (ISAF) said in a statement.

In NATO terms, southwestern Afghanistan includes Nimruz and Helmand provinces, where nearly 20,000 US Marines are stationed.

While helicopter crashes occur with some regularity in Afghanistan, ISAF says they are rarely the result of Taliban fire.

On March 16, 12 Turkish soldiers and two civilians were killed in a chopper crash in the Afghan capital Kabul.

In January, six US troops were killed in a CH-53 Sea Stallion helicopter crash in the Musa Qala district of Helmand province.

And 30 US troops and eight Afghans were killed in August 2011 when Taliban insurgents shot down a Chinook helicopter, in the deadliest incident for US and NATO forces since the war in Afghanistan began in 2001.

Technology gives viral edge to soldiers' frontline snapshots
Washington (AFP) April 18, 2012 - Soldiers posing with slain or captive foes for trophy pictures is nothing new. What is new, experts said Wednesday, is how technology is enabling such images to go viral.

Digital photography makes snapshots like those of US soldiers alongside the mangled remains of Taliban suicide bombers reveal a brutal side of conflict that's disturbing to civilians, but all too familiar to combatants.

"There have been snapshots since the Boer War," said curator Anne Wilkes Tucker, who is overseeing an upcoming major exhibition on war and photography at the Museum of Fine Arts in Houston, Texas.

"I've seen German snapshot albums from World War One and Two that have execution pictures," Tucker told AFP in a telephone interview. "I mean, these are soldiers' photographs that I guess you brought home to Mom."

But such images, shot on film that needed time to be developed and printed, were typically shared within a tight inner circles. Others might not see them for many years -- if at all.

Compare that to how today's warrior can knock off some shots with a cellphone or pocket-size digital camera, email them to comrades and family -- and potentially, if unwittingly, see them wind up in the public domain.

"The distribution is what has changed," Tucker said.

"Most soldiers have access somewhere to the Internet," enabling them to instantly download their unique view of the battlefield, added Matthew Seelinger, chief historian at the independent Army Historical Foundation.

The White House and NATO on Wednesday condemned snapshots -- obtained by The Los Angeles Times -- of US paratroopers posing with the severed hand and disembodied legs of Afghan suicide bombers that they had gone out to inspect.

NATO secretary general Anders Fogh Rasmussen dismissed the images as "an isolated event," but they recalled the release in January of online video clips showing US marines urinating on the bodies of Afghan fighters.

They also harked back to photos of US soldiers abusing Iraqi detainees at Abu Ghraib prison in Baghdad in 2004, and those of a US army "kill team" that came to light in March 2011 in the German newsmagazine Der Spiegel.

As it happens, 2004 was the same year that a group of Israeli soldiers triggered an uproar with an exhibition of their own, often unsettling snapshots from the Second Intifada on the occupied West Bank.

"Just like you take photographs of your life, we took photographs of our life," said one of the soldiers, Yehuda Shaul, a co-founder of Breaking the Silence, a group that raises public awareness of what Israeli troops face on the front lines.

"If you were a mountain climber and you reached the top of Everest, you would take a photo," he told AFP by telephone from Israel.

"When you are trained as a combat soldier, you are trained to kill your enemy -- and when you do that, don't expect me not to take a souvenir."

Shaul did not condone such conduct, but he said it was "hypocrisy" for society to send soldiers into conflict, then blame them individually if their personal depictions of reality turn out to be so troubling.

"It is their life at the moment," concurred Tucker, who has spent eight years sifting through 165 years' worth of war images for the "War/Photography: Images of Armed Conflict and Its Aftermath" show that opens in November.

"With pictures like this, we have to remind ourselves that we sent them there to do this."