Israel struck a defiant tone Tuesday over its lethal takeover of a humanitarian flotilla bound for the Gaza Strip, saying it had nothing to apologize for even as much of the world called for an end to its three-year blockade of the coastal Palestinian enclave.

Israel's hard-line response came as organizers of the flotilla said they were sending another ship to attempt to break the longstanding siege, which began after the militant group Hamas took control of Gaza in 2007.

The border restrictions were partly lanced Tuesday, when Egypt, facing diplomatic pressure from fellow Muslim nations, announced that it would open its own crossing into Gaza at Rafah to allow shipments of humanitarian supplies.

Meanwhile, activists released by Israel began issuing their eyewitness accounts of the confrontation at sea. The initial firsthand versions had come almost exclusively from the Israeli government, which jammed communication with the flotilla and incarcerated most of the activists once ashore. Israel's military released video it said showed its commandos being attacked onboard the Mavi Marmara, a Turkish ship leading a Turkish-sponsored convoy, by activists armed with sticks and other weapons. It said its commandos fired live rounds only in self-defense.

On Tuesday, the captain of one of the other ships in the flotilla, Huseyin Tokalak, said Israeli ships opened fire on the Mavi Marmara before boarding that ship, according to Reuters news agency. He also said Israel had threatened to sink his ship unless commandos were allowed to board and take control. "They started shooting directly at Mavi Marmara. They didn't care if it was the front or back of the ship," Reuters quoted Tokalak as saying.

The emergence of contrasting versions of the melee at sea fueled calls for an independent international inquiry. The White House appeared receptive to proposals for some form of investigation, issuing a statement Tuesday saying that President Obama offered U.S. support for "a credible, impartial, and transparent investigation of the facts," during a condolence call to Turkish Prime Minister Recep Tayyip Erdogan.

Israeli government officials have not indicated whether they intend to open a formal inquiry. Prime Minister Benjamin Netanyahu, who returned hastily to Israel from Canada after canceling Tuesday's planned White House meeting with Obama, made only brief statements, defending the raid and saying his administration has no plans to alter its policy toward Gaza.

"We have a simple policy, which will continue," the prime minister said.

Israel says a continuing siege is needed to prevent Hamas from receiving weapons and foreign support from Iran and other anti-Israel countries. In recent months, Israel has allowed trucks to cross into Gaza with limited amounts of clothing and cement; many food items and essential goods are available, but many families cannot afford to pay for them.

Deputy Foreign Minister Danny Ayalon scoffed at calls for Israel to apologize, saying flotilla activists prompted the violence by attacking soldiers during the raid. "We do not need to apologize for defending ourselves," he said.

But Israel did say it would release — and deport — the 680 activists it had arrested. And as international criticism of the raid swelled, the public mood appeared to shift in Israel as well, with many questioning whether the botched predawn raid on a ship in international waters was worth the damage to the country's image.

Israeli newspaper headlines on Tuesday used language such as "fiasco" and "flawed policy" to describe what they saw as a poorly planned mission and clumsy handling of the political aftermath, with some calling upon Defense Minister Ehud Barak to resign.

And some voices inside Israel were raised against continuing the cordon around Gaza. Imposed in response to the Hamas takeover of the territory and the kidnapping of Israeli soldier Gilad Shalit, who is still being held in Gaza, the naval blockade and border restrictions have failed to bring about Shalit's release or to force Hamas from power.

Meanwhile, 1.5 million Gazans struggle to survive on the limited amount of aid passed through Israeli screening and whatever can be smuggled in through a network of tunnels. A policy that was initially aimed at isolating Hamas has instead largely isolated Israel, many analysts say, noting that the country has been frequently criticized by the United Nations and the European Union, as well as by the U.S. and numerous other countries, for preventing enough food and medical supplies from reaching Gaza.

"We are no longer defending Israel," wrote columnist Bradley Burston in Haaretz, a leading Israeli newspaper. "We are now defending the siege. The siege itself is becoming Israel's Vietnam."

The sharpest breach in Israel's alliances appeared to be with Turkey, one of its few friends in the Muslim world but a nation with which it has seen deteriorating relations since the Jewish state's 2008-09 offensive in Gaza. Monday's deaths at sea occurred aboard the Mavi Marmara. At least four of the nine dead activists are believed to be Turkish citizens.

On Tuesday, Erdogan, the Turkish prime minister, called the raid a "bloody massacre" and told his country's parliament that "nothing will be the same again." Erdogan's support for the pro-Palestinian flotilla contributed to his rising reputation among Israel's critics in the Middle East, many of whom have become disillusioned with the ability of longstanding regional leaders such as Egyptian President Hosni Mubarak to improve conditions for the Palestinians.

Turkish anger was also apparent in Washington, where Foreign Minister Ahmet Davutoglu complained that the Obama administration had watered down a Security Council statement negotiated Monday night in New York. The 15-member council issued a carefully crafted condemnation, which criticized "acts" of violence but did not specifically condemn Israel.

Turkey and others lobbied for stronger language, including demands for an international inquiry into the raid, but accepted the vaguer language in order to secure U.S. support.

"We expect full solidarity with us," Davutoglu said. "It should not be a choice between Turkey and Israel. It should be a choice between right and wrong."

But Israel rejected the Security Council statement. Foreign Minister Avigdor Lieberman telephoned U.N. Secretary-General Ban Ki-moon to complain about what he called the international community's "hypocrisy and double standards" in dealing with Israel, terming the U.N. statement "unacceptable."

On Tuesday, the Obama administration appeared — at least initially — to suggest that Israel could conduct an impartial inquiry into the events on its own.

"We support an Israeli investigation that meets those criteria," said Secretary of State Hillary Rodham Clinton, adding that the administration was "open to different ways of ensuring a credible investigation, including international participation."

Some Israelis matched those calls for a quick, Israeli-driven inquiry to avoid a repetition of what happened after the international criticism that followed Israel's Gaza offensive 17 months ago.

After Israel resisted pressure to allow an independent investigation of its military's conduct, a U.N. commission was created, led by South African jurist Richard Goldstone. Its report, which concluded that Israel deliberately targeted civilians during the assault, left the Israeli public bitter and deeply divided.

Haim Oron, a member of parliament from the left-leaning Meretz party, said the only way for Israelis to "save ourselves" and avoid another Goldstone report was to quickly set up a national commission to examine the attack.

"It would be best for us to say from Day One that we are investigating what happened," Oron told Israel Radio. "No flotilla could cause Israel the kind of damage we inflict on ourselves time after time with mistaken decisions."

Israelis also have unanswered questions about the raid itself. Why was Israel's most elite squad of naval commandos deployed to seize a humanitarian vessel? How could such highly trained military personnel be so unprepared for, or so quickly overcome by, pro-Palestinian activists, who managed to throw one commando off the deck? And would Israel's security have been more or less compromised by allowing the vessels to dock and unload their cargoes in Gaza than it has been by the international outcry?

The answers may have to come soon. Leaders of the Free Gaza Movement, which organized the flotilla, say they are still determined to attempt to break the siege with a cargo ship that is already in the Mediterranean.

They have not decided when to set sail for Gaza, but the ship is expected to arrive off Israel in the next week.

Israeli officials have vowed to intercept it.