Al-Qaeda in Iraq said for the first time on Tuesday that Al-Nusra Front, a jihadist group battling President Bashar al-Assad's regime, was part of its network and fighting for an Islamic state in Syria.
The remarks by the leader of Al-Qaeda's front group in Iraq, Abu Bakr al-Baghdadi, were made in an audio message posted on jihadist forums and confirm widespread suspicions of links between the two groups.
"It is time to declare to the Levant and to the world that the Al-Nusra Front is simply a branch of the Islamic State of Iraq," Baghdadi said in the audio message.
The groups will now be combined and called the Islamic State in Iraq and the Levant.
Baghdadi said the group was willing to ally with other groups "on the condition that the country and its citizens be governed according to the rules dictated by Allah".
Al-Nusra Front first gained notoriety for its suicide bombings in Syria but has evolved into a formidable fighting force leading attacks on battlefronts throughout the country.
Its suspected affiliation to Al-Qaeda's front group in Iraq led to it being labelled a "terrorist" organisation by Washington in December.
At the time, the US State Department described it as a "new alias" for Al-Qaeda in Iraq, and said it was "an attempt by AQI to hijack the struggles of the Syrian people for its own malign purposes".
According to the US, the head of Al-Qaeda in Iraq "is in control of both AQI and Al-Nusra" and reports on Internet forums used by jihadists indicate hundreds of militants have made the trip from Iraq into Syria to fight Assad's regime.
Syria's conflict, now in its third year, is believed to have killed more than 70,000 people since it erupted in March 2011.