ABOARD A U.S. MILITARY AIRCRAFT (Reuters) - Defense Secretary Robert Gates criticized the Internet group Wikileaks on Tuesday over its release of a video showing a 2007 U.S. helicopter attack that killed a dozen people in Baghdad, including two Reuters news staff.

This image captured from a classified U.S. military video footage shows a van being attacked by U.S. Apache helicopters that killed a dozen people in Baghdad, including two Reuters news staff on July 12, 2007 and released to Reuters on April 5, 2010 by WikiLeaks, a group that promotes leaking to fight government and corporate corruption. REUTERS/WikiLeaks/Handout

The group, which says it promotes leaks to fight government and corporate corruption, released the video without providing any context explaining the situation, Gates said.

“These people can put out anything they want, and they’re never held accountable for it. There’s no before and there’s no after,” Gates said.

The stark helicopter gunsight video of the July 12, 2007, attack has been widely viewed around the world on the Internet since its release on April 5.

Some international law and human rights experts say the Apache helicopter crew in the footage may have acted illegally. The video includes an audio track of a helicopter crew conversation. Many have been shocked by the images and some of the fliers’ comments.

The U.S. military said an investigation shortly after the incident found U.S. forces were unaware of the presence of news staff and thought they were engaging armed insurgents, mistaking a camera for a rocket-propelled grenade launcher.

“We take these things seriously,” Gates said, in reference to civilian casualties.

The Reuters staff killed in the attack were photographer Namir Noor-Eldeen, 22, and his assistant and driver Saeed Chamagh, 40.

Wikileaks disputed Gates’ contention the video failed to provide context. In an e-mail, it accused the U.S. military of making “numerous false or misleading statements,” including the contention there was an active firefight between U.S. forces and those killed.

“Classified records which we will shortly release show that there was a report of small arms fire at 9:50 a.m., somewhere in the suburb of New Baghdad, shooter and location UNIDENTIFIED. There is no reference to U.S. forces having been hit by the fire. The same records report that at 10:18, 28 minutes later, the crowd was seen and the killing commenced.”

The e-mail was unsigned but was sent from the press office e-mail of Wikileaks.