The head of Syria's jihadist Al-Nusra Front has pledged allegiance to Al-Qaeda chief Ayman al-Zawahiri, but distanced his group from claims it has merged with Al-Qaeda in Iraq.
Al-Nusra's announcement on Wednesday is likely to bolster assertions by President Bashar al-Assad's regime that it is fighting "terrorists" who want to impose an Islamic state.
"The sons of Al-Nusra Front pledge allegiance to Sheikh Ayman al-Zawahiri," Abu Mohammed al-Jawlani said in a recording.
But, he added, "we were not consulted" on a claim by Al-Qaeda in Iraq chief Abu Bakr al-Baghdadi on Tuesday of a merger with Al-Nusra.
"We inform you that neither the Al-Nusra command nor its consultative council, nor its general manager were aware of this announcement. It reached them via the media and if the speech is authentic, we were not consulted."
Jawlani stressed his group would not change.
"Al-Nusra Front will not change its flag, though we will continue to be proud of the flag of the Islamic State of Iraq, of those who carry it and those who sacrifice themselves and shed their blood for it," said Jawlani, acknowledging he had fought in Iraq alongside the ISI, Al-Qaeda's Iraqi offshoot.
Jawlani's comments came a day after the ISI announced Al-Nusra was part of its network, confirming long-held suspicions that led the United States to put the group on its terror blacklist.
The announcement followed a message from Zawahiri, urging rebels to fight to establish an Islamic state in Syria, and was received with caution by the mainstream rebel Free Syrian Army.
"We don't support the ideology of Al-Nusra," FSA spokesman Louay Muqdad told AFP.
Al-Nusra is among the most prominent organisations involved in Syria's conflict, which erupted in March 2011 with peaceful protests against Assad's regime but has evolved into a war that has killed tens of thousands.
It has gained notoriety for suicide bombings but also won admiration from some insurgents for its reputation as a formidable fighting force leading attacks on battle fronts across Syria.
Baghdadi's statement raised suspicion among anti-Assad activists in Syria, said Abu Nadim, who lives in rebel-held Douma near Damascus.
"When Al-Nusra Front first appeared on the scene, we didn't know much about it. Now people know what it's about, and many have condemned attacks that targeted civilians," Abu Nadim told AFP via the Internet.
"We will not accept any group imposing its ideology. Who says we want to build an Islamic caliphate, or that we're even thinking about that, while Syria is burning?"
The West has been wary, and the announcements this week are likely to complicate any attempt to arm the rebels.
The US and EU are now providing non-lethal aid to the rebels, but Britain and France want an EU arms embargo on Syria lifted so they can supply the rebels with weapons.
Despite the announcements, a group of pro-opposition government representatives, including US Secretary of State John Kerry, would meet next week in Istanbul to discuss Syria, a US State Department official said, asking not to be identified.
In London, Syrian opposition leaders met with Kerry on the sidelines of the G8 talks, where they renewed appeals to be supplied with arms without going into specifics.
But Kerry "didn't promise anything" to them, said a second State Department official who also asked not to be identified.
In Syria on Wednesday, Kurdish fighters expelled regime troops from part of the majority Kurdish city of Hasake, the Syrian Observatory for Human Rights reported.
As violence raged across the country, at least 98 people were killed, said the Observatory.
Human Rights Watch in a new report accused the Syrian regime of killing more than 4,300 civilians in air strikes across Syria since July 2012.
"Syrian government air strikes that have deliberately or indiscriminately killed civilians appear to be part of systematic and widespread attacks against the civilian population that Human Rights Watch previously found amount to crimes against humanity," it said.
Basing its findings on investigations in rebel-held areas of three war-torn provinces, the New York-based group documented air strikes on four bakeries and two hospitals, along with other civilian targets.