A senior Pakistani security official said US troops killed Osama bin Laden in "cold blood", fuelling a global controversy and straining a vital relationship Washington was trying to repair on Thursday.
And Pakistan's army, in its first comment since Monday's raid, threatened to halt cooperation with its military sponsor if it repeated what it called a violation of sovereignty.
But US Secretary of State Hillary Clinton said Washinton was still anxious to maintain its alliance with Islamabad.
"It is not always an easy relationship. You know that," she said.
"But, on the other hand, it is a productive one for both our countries and we are going to continue to cooperate between our governments, our militaries, our law-enforcement agencies, but most importantly between the American and Pakistani people."
Americans are questioning how the al Qaeda leader could live for years in some comfort in a garrison town near the Pakistani capital. Some call for cutting billions of dollars in U.S. aid.
As Clinton was meeting European and Arab allies in Rome, Pakistan's Chief of Army Staff, General Ashfaq Kayani, issued a statement saying any new U.S. raids would mean a possible end to cooperation with the Pentagon on security and intelligence.
"Any similar action violating the sovereignty of Pakistan will warrant a review on the level of military/intelligence cooperation with the United States," the army said.
And in a further sign of fractious relations between the allies, senior Pakistani security officials told Reuters that U.S. accounts had been misleading in describing a long gun battle at the compound in Abbottabad where bin Laden and four others were killed by an elite squad of US Navy SEALs.
"It was cold-blooded," said one Pakistani official when asked if there was any exchange of fire. After an initial account of a 40-minute firefight, U.S. officials have now been quoted saying only one person fired at the raiding party, and that only briefly as the helicopter-borne assault team arrived.
A US acknowledgment that bin Laden was unarmed when shot in the head -- as well as the disposal of his body at sea, a practice rare in Islam -- have drawn criticism from the Arab world and Europe, where some have warned of a backlash against the West, even among Muslims who reject Qaeda's violence.
Bin Laden unarmed
The White House has blamed the "fog of war" for its changing stories. Citing US officials, NBC television said four of the five people killed, including bin Laden himself, were unarmed.
The New York Times quoted officials in the administration of President Barack Obama saying bin Laden's courier fired the only shots against the Americans, in the early stages of the raid, from a guesthouse in the sprawling, high-walled compound.
"I know for a fact that shots were exchanged during this operation," said one Pentagon official.
Another senior Pakistani security official said no shots were fired inside the building where bin Laden was found.
"The people inside the house were unarmed. There was no resistance," the official said.
The two Pakistani officials declined to describe the sources of their information but confirmed several people from the compound were detained.
Pakistan's GEO TV quoted military sources saying bin Laden's Yemeni-born wife told them the Saudi-born al Qaeda leader had lived in Abbottabad for five years but had never ventured out.
Photographs taken by a Pakistani security official about an hour after the assault show three dead men -- not including bin Laden -- lying in pools of blood. No weapons could be seen in the closely cropped images obtained by Reuters.
Friction between Washington and Pakistan, a nuclear-armed Muslim ally in the war in Afghanistan and against al Qaeda, has focused on the role of Pakistan's top security service, the ISI or Inter-Services Intelligence Directorate.
With questions swirling about how far it was incompetence or connivance that allowed bin Laden to shelter so close to a major military academy, Pakistan's leaders and security officials have defended their roles and their commitment to the U.S. alliance.
Foreign Secretary Salman Bashir denied the Pakistani forces or ISI aided al Qaeda: "The critique of the ISI is not only unwarranted, it can not be validated," he said, echoing comments from the prime minister who blamed global intelligence failures.
Some Americans, including many in Congress, have suggested that Washington attach more strings to the billions of dollars in aid it gives Pakistan, or even cut off Islamabad altogether.
Bashir said: "That the ISI is incompetent is a value judgment. And we believe that this is not the time for anybody to indulge in the luxury of passing value judgments."
He also issued a warning -- seemingly directed as much at arch-rival India as to Washington -- against intrusions of the kind that saw U.S. troops raid deep inside Pakistan. While few in Pakistan supported bin Laden and his ideology, violations of sovereignty can provoke street protests and media outrage.
A major Islamist party in Pakistan, Jamaat-e-Islami (JI), called for mass protests on Friday against what it called a violation of sovereignty by the U.S. raid. It also urged the government to end support for U.S. battles against militants.
From abroad, China spoke up for Pakistan on Thursday: "Pakistan is a country at the forefront of counter-terrorism efforts, and the international community should give greater support and understanding," a foreign ministry spokeswoman said in Beijing. "We respect and understand Pakistan's stance."
"38 intense minutes"
Washington has repeatedly defended its decision to kill bin Laden, though in fact foreign criticism of its failure to take him alive has not been heard in public from the leaders of its key allies in the battle against militant Islam.
In Rome for talks on aiding Libya's rebels, Clinton reminded her international audience that bin Laden had been a clear target for the United States since 2001 and that his death did not end the battle against al Qaeda.
She refused to comment on details of the operation, which she had watched unfolding on a live video transmission.
"Those were 38 of the most intense minutes," she said, referring to a photograph that caught her looking anxious during the raid. She put her gesture down to suppressing a cough.
Aside from defending its forces from criticism from abroad -- Attorney-General Eric Holder has called the shooting of bin Laden "an act of national self-defence" -- the United States has also had to counter those who question the death altogether.
Obama resisted pressure from aides to release photographs of bin Laden's body, saying the images could incite violence and be used by militants as a propaganda tool.
"Given the graphic nature of these photos, it would create some national security risk," Obama told CBS television.
"There's no doubt that bin Laden is dead," he added. "There are going be some folks who deny it. The fact of the matter is, you will not see bin Laden walking on this earth again."