One of the nine people killed in an Israeli commando raid on a flotilla of ships heading for Gaza this week was a United States citizen of Turkish descent, according to officials in Turkey and Washington.

The development added a new diplomatic complexity as Israel struggled to defuse rising international anger over its raid on six ships seeking to break its blockade of the Gaza Strip, where officials from the Hamas movement were reported on Thursday to be resisting Israeli efforts to deliver truckloads of goods seized from the flotilla.

The bodies of the nine dead were flown back to Turkey overnight along with hundreds of activists, many of them Turks, who had been detained when the Israeli navy towed the ships to shore on Monday. Israel resolved on Wednesday to release nearly all of the detainees quickly — including those suspected of attacking its soldiers as they boarded — to prevent further diplomatic damage.

But, as coffins bearing the dead wound through a devout neighborhood of Istanbul, accompanied by thousands of Turkish mourners, public anger here seemed undiminished.

“Turkey will never forgive this attack,” President Abdullah Gul said on NTV television. “Turkish-Israeli relations can never be as before from now on.”

A senior Turkish official, who spoke in return for anonymity under government rules, said Turkish investigators examining the dead had found that one of them was an American of Turkish descent, but did not identify the American by name. A United States official in Washington confirmed that an American was among the dead.

Reports in the Turkish press identified the American as Furkan Dogan, a 19-year-old who was born in the United States and lived there for four years before returning to Turkey with his family.

Mr. Dogan’s brother, Mustafa, described him as “clean hearted with a happy face,” and said that he had asked for his parents’ blessing before leaving with the flotilla, according to a report in the Turkish daily Zaman.

“We didn’t expect him to come back like this,” Mr. Dogan’s brother was quoted as saying. “However, we were not sorry to hear that he fell like a martyr.”

The Cihan news agency reports that Mr. Dogan had one bullet in the chest and four bullets fired into his head from close range.

Israel has attributed blame for the confrontation on activists who assaulted Israeli commandos as they dropped on ropes from helicopters onto the biggest of the vessels, the Turkish-owned Mavi Marmara.

The United Nations has called for a full international inquiry into the raid, but on Thursday, Israeli officials rejected that demand in favor of a narrower, internal investigation, news reports said. Earlier on Thursday, planes carrying hundreds of activists, along with the nine dead, flew to Turkey and Greece, as others were released through Jordan.

Hours later, thousands of mourners flooded onto a main thoroughfare to escort the coffins draped in Turkish and Palestinian banners to the Edirne Kapi graveyard, which is usually reserved for those fallen in battle.

“God is great,” mourners chanted in Arabic along with Turkish slogans saying, “Damn Israel,” “an eye for an eye, blood for blood, revenge, revenge.” A woman in a black T-shirt, jeans and sunglasses wore a green headband with the motto in Arabic: “We are all Palestinians now,” echoing statements made after the Sept. 11 attacks in the United States when some Europeans proclaimed that they were “all Americans now.”

Many waved the green banners associated with Islam, by far the predominant faith in Turkey.

The Israeli Foreign Ministry said on Thursday that all the activists had been deported except for seven in hospital recovering from injuries, the wife of one of the injured and two others who had been held up for reasons relating to documentation.

After it seized the ships, Israel said it would deliver the aid goods the activists said they were trying to bring to Gaza.

But, said Maj. Guy Inbar, a senior Israeli official, the Hamas authorities were not allowing supplies from the ships to enter Gaza on Thursday. Eight truckloads of goods had been unloaded at a crossing point between Israel and Gaza and 13 more trucks were waiting, he said.

Hamas officials were quoted as saying they were refusing to accept the goods until all of the detainees had been freed.

Even as Israel sought to improve its international standing with the quick prisoner release, it again defended the raid. Prime Minister Benjamin Netanyahu, in a television address on Wednesday night, said the blockade was necessary to prevent rockets and missiles from being smuggled to Hamas, which governs Gaza, and other anti-Israel militants.

“Opening a naval route to Gaza will present enormous danger to the security of our citizens,” he said. ‘Therefore, we will stand firm on our policy of a naval blockade and of inspecting incoming ships.”

There was no telling if Israel’s gesture in releasing the detainees would be enough to roll back longer-term damage to Israel’s relationships, especially with Turkey, which has grown increasingly angry at Israel.

Worries also persisted about the impact of the confrontation on the shaky Middle East peace effort. George J. Mitchell, the United States special representative to the region, said Thursday that the fallout from the raid should not derail the indirect negotiations he is mediating between Israelis and Palestinians, Reuters reported.

“This incident underscores to need to make progress in negotiations,” Mr. Mitchell said in the West Bank town of Bethlehem.

The uproar was ignited when Israel sent its commandos into international waters to stop the flotilla carrying humanitarian aid, including construction materials, toys and used clothes, to Gaza. Commandos boarded five ships without incident, but when they dropped from helicopters onto the largest, the Mavi Marmara, soldiers opened fire when they said they were attacked by passengers with chains, knives, bars and clubs.

It appears unlikely the conflict will fade soon. With at least one new ship already setting sail to challenge the sea blockade, another flotilla being planned in London, the United Nations Human Rights Council in Geneva voting to create a committee of investigation and the world body’s secretary general, Ban Ki-moon, saying Israel’s policy “punishes innocent civilians,” Israeli officials maintained they would not relent.

The dual images of Turkey as a guardian of Palestinian rights, and Israeli soldiers shooting unarmed civilians, undermined the credibility of Arab capitals allied with the West, regional foreign policy experts said. Egypt, Jordan and Saudi Arabia, which have pressed for a comprehensive peace with Israel, were placed on the defensive as Turkey, allied with Iran, Syria and Qatar, has gained credibility through its support of Hamas.

Egypt felt so exposed by the events at sea that it opened the border between Gaza and Rafah. Egypt has withstood criticism for keeping its border mostly closed, even during the 2008 Israeli invasion in Gaza. Egypt has argued that opening the border would undermine its own security and leave it as the de facto administrator of Gaza. Egypt also does not want a Hamas-ruled enclave on its border, fearful it will spread the group’s militant Islamic ideology over the border. Still on Wednesday the border was opened. More than 600 people crossed into Egypt from Gaza.

The crisis is the latest in a series of Israeli decisions devised to secure the nation, and while each was to some degree tactically successful, each also further undermined its international legitimacy and increased its international isolation, policy experts here said. Those actions included building a barrier along the border with the West Bank to keep out suicide bombers; bombing Lebanon to try to disarm Hezbollah; invading Gaza in response to Hamas rocket fire; and blockading Gaza to keep out weapons.

Yaacov Bar-Siman-Tov, a professor of international studies at Hebrew University, said the nation’s leadership had failed to improve its problem with legitimacy because it focuses on tactics, like destroying enemies, rather than on a long-term strategy aimed at an ultimate settlement with the Palestinians.

“What would we like to achieve here?” Mr. Bar-Siman-Tov said. “If you would like to keep the Jewish state we have to be separated from the Palestinians. There is no way to continue with the occupation. It has created damage to our credibility and legitimacy.”