Israeli naval forces stormed a Gaza-bound aid flotilla in international waters before dawn on Monday, killing up to 19 pro-Palestinian activists, most of them reportedly Turkish nationals.
The bloody ending to the high-profile mission to deliver supplies to the besieged Gaza Strip plunged Israel into a diplomatic crisis on the eve of talks between President Barack Obama and Israeli Prime Minister Benjamin Netanyahu.
As Israel pointed the finger of blame at passengers for initiating the violence, accusing them of using deadly force, activists from the ships countered with their own descriptions of how events unfolded in raid which took place in international waters at around 5am (12:00 AEST).
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Live footage taken from the Turkish passenger boat, which was posted all over the internet, showed black-clad Israeli commandos rappelling down from helicopters and clashing with activists, as well as several wounded people lying on the deck of the ship.
"Under darkness of night, Israeli commandos dropped from a helicopter onto the Turkish passenger ship, Mavi Marmara, and began to shoot the moment their feet hit the deck," according to a report on the website of the Free Gaza Movement.
The shaky footage shows scenes of chaos, with the dark profiles of Israel missile boats looming in the background.
The Israeli army insisted its troops opened fire only after they were attacked with knives, clubs and even live fire.
Fairfax Journalist Paul McGeough and photographer Kate Geraghty were out of communication for some hours after the clash, sparking concern for their welfare.
"We are pleased to report that Paul McGeough and Kate Geraghty, who are among the most experienced and well-trained Australian foreign correspondents, are safe, and being processed in an Israeli detention centre," Sydney Morning Herald Editor in Chief Peter Fray said.
"We remain hopeful that they will be allowed to do their job, and that they will have a terrific story to tell when they are released."
Mr Fray said his company had made representations to the Israeli and Australian governments seeking safe passage for the pair.
Unconfirmed media reports from Hamas' Al Aqsa television said up to 20 passengers had been killed, of whom nine were Turkish nationals.
Israeli private channel 10 television reported that Israeli marine commandos had opened fire after being attacked with axes and knives by a number of the passengers on board the aid ships. It did not give the source of its information.
It was not clear whether the clashes took place on just one of the six boats making up the aid convoy.
Hamas-run Al-Aqsa television showed footage of black-clad Israeli commandos descending from helicopters and clashing with activists, as well as several wounded people lying on the deck of the ship.
Israeli Defence Force radio was reporting passengers on board the aid-laden convoy of boats tried to wrest weapons from Israeli soldiers, The Jerusalem Post reported.
The Free Gaza organisation said on Twitter that its lawyer in the northern Israeli coastal city of Haifa said 10 people had been killed.
The group said the boats were being taken into Haifa by the Israeli Defence Force (IDF).
A Turkish diplomat said the Israeli ambassador was summoned to the Turkish foreign ministry today after a Turkish aid ship was stormed.
"The ambassador [Gabby Levy] was summoned to the foreign ministry. We will convey our reaction in the strongest terms," the diplomat, who asked not to be named, told AFP.
Meanwhile in Turkey, local media is reporting police have blocked dozens of stone-throwing protesters who tried to storm the Israeli consulate in Istanbul following the flotilla attack.
CNN-Turk and NTV televisions showed dozens of angry protesters scuffling with Turkish police, who are guarding the consulate in downtown Istanbul.
The protesters were shouting "damn Israel", the Associated Press reported.
The ships, carrying more than 700 passengers, were on the last leg of a high-profile mission to deliver about 10,000 tonnes of building and other supplies to Gaza, which has been under a crippling Israeli blockade since 2007.
Huwaida Arraf, chairwoman of the Free Gaza Movement, told AFP earlier by phone from the boat Challenger 1 that the ships had expected a confrontation with Israel today.
The boats had started heading towards Gaza from international waters of Cyprus at 3pm local time (1200 GMT) on Sunday, with organisers saying they hoped to enter Gaza waters during the daylight hours.
About six hours after their departure, three Israeli missile boats left their naval base in Haifa on a mission to intercept the flotilla, reporters on board one of the vessels said before being told to turn off their phones.
Israel has slammed as "illegal" the convoy's attempt to break the Gaza blockade and warned it would intercept the ships, tow them to the port of Ashdod and detain the activists before seeking to deport them.
In Gaza, anti-siege activists on Sunday called on the international community to ensure the protection of the flotilla, which had been aiming to arrive on Saturday but was repeatedly delayed.
"I am asking the international community to protect these boats from the Israeli threat," independent Palestinian MP Jamal al-Khudari told a news conference on a boat anchored outside the Gaza port.
"If Israel blocks them, they have a strategy for getting here," said Mr Khudari, who heads the Gaza-based Committee to Lift the Siege. He did not elaborate.
With the flotilla expected to approach at some stage over the next 24 hours, Gaza fishermen took to the sea flying Palestinian flags as well as those of Greece, Ireland, Sweden and Turkey - all of which sent boats.
Demonstrators also released scores of balloons with pictures tied to them of children killed during Israel's massive 22-day offensive against Gaza that ended in January 2009.
Mr Khudari said the convoy, which is carrying hundreds of civilians and a handful of European MPs, would stop outside Gaza territorial waters before attempting to make landfall.
It will travel "in two stages", he said: "First they will stop in international waters at 30 nautical miles [from Gaza], and tomorrow [Monday] they will reach the shore."
Audrey Bomse, legal adviser to the Free Gaza Movement, said the activists were considering sending "a second wave" of boats later this week.
Israel has called the convoy a media stunt, insisting the humanitarian situation is stable in Gaza despite reports to the contrary from aid agencies and offering to deliver the supplies through its own land crossings.
"This is a provocation intended to delegitimise Israel," Deputy Foreign Minister Danny Ayalon said on Saturday.
"If the flotilla had a genuine humanitarian goal, then its organisers should have transferred something for the abducted soldier Gilad Shalit as well," he said of the Israeli snatched by militants in 2006 and held by the Hamas Islamist movement, which runs the enclave.
The activists responded on their website that they had offered to take in a letter for the soldier from his family but received no response from their lawyer.
Hamas's refusal to release Mr Shalit is cited by Israel as one of the main reasons for imposing the economic blockade on Gaza in the wake of the group's violent takeover of the territory.
Pro-Palestinian activists have landed in Gaza five times, with another three unsuccessful attempts since their first such voyage in August 2008. The latest is their biggest operation.