Blasts from a megaphone accompany the sounding of alarms, a woman's voice repeatedly pleading, "We are civilians, we have no guns...we need help for people...please don't attack."

Brazilian-American filmmaker Iara Lee, a passenger on board the Mavi Marmara, managed to smuggle an hour of footage taken during the May 31 attack on a six-ship humanitarian flotilla bound for Gaza by the Israeli Defence Forces. An activist from the group Cultures of Resistance, Lee released her footage to the press Thursday at the United Nations. She plans to make it available to the public, to let the images speak for themselves.

The footage starts before the attack, with the sounds of a passenger chanting prayers, while others kneel in observance of prayers. Later, it features gripping images of wounded passengers, along with passengers bearing metal poles and slingshots targeted at the helicopters flying above.

Attempts were made to reroute the ship to avoid confrontation when those aboard realised that Israeli vessels were approaching, Lee said.

"We were not mentally prepared," she said. "We thought we would have had some sort of verbal confrontation, or a shot in the foot."

Both sides charge that video and audio images have been altered or selectively edited to corroborate the clashing accounts of what occurred.

The Israeli government released doctored footage to support the accounts of soldiers involved in the raid, which seemed to indicate they had been beaten with metal rods and chairs upon boarding. Meanwhile, Reuters has defended its cropping of images that conceal a knife-wielding passenger and a wounded soldier as inadvertent, an editing error.

Israeli soldiers claim they had acted in self-defence, while Pro-Palestinian campaigners say they did nothing to provoke the violence that led to nine passenger deaths, and were not in possession of deadly weapons. The footage released by Lee appears to confirm elements of both accounts - that passengers wielded metal poles and slingshots, while the soldiers who stormed the ships used excessive force.

Edward Peck, a former U.S. diplomat and vocal critic of U.S. policy toward Israel, was also a passenger, as a member of the Free Palestine Movement, and witnessed the unfolding of the raid. He told IPS they had planned to offer passive resistance. "I don't think anyone expected bloodshed," he said.

Asked if it was possible passengers on board were wielding any kind of weapons, he said, "I don't know if they had them, some people would say they were justified in using them - the Israeli force was overwhelming and unhesitating."

Israeli authorities confiscated most of the audio and visual evidence gathered by the dozens of journalists who had accompanied the activists to report on their stated intention of breaching the blockade imposed since 2007, following the de facto rule of Hamas over the Gaza Strip.

Lee's footage also captured a passenger on board who was able to get a hold of a document carried by soldiers that she interpreted as a list of high-profile passengers. It contained pictures of a member of parliament from Sweden and Former Jerusalem Archbishop Hilarion Capucci, Lee said. She speculated that perhaps it was a list of people who should not be harmed.

Altogether, the flotilla had about 700 passengers, including 60 journalists.

U.N. Secretary-General Ban Ki-Moon has called for a "prompt, credible, impartial and transparent investigation" with an international element. Ban has consulted with his legal counsel to solicit an assessment and advice, but has not made a statement confirming whether the soldiers contravened the Charter on the Law of the Sea.

The Israeli government has yet to accede to these terms, and negotiations continue on the framework for an investigation. The Israeli Defence Forces have reserved the right to be the only ones to question their soldiers - as is the protocol with armies worldwide - and Prime Minister Binyamin Netanyahu has issued a statement invoking this right.