Beirut: Seven key Islamist groups fighting President Bashar al-Assad`s regime in Syria announced a merger to form an "Islamic Front" on Friday, pledging to work towards an Islamic state.
"The Islamic Front is an independent military and social force that is aimed at bringing down Assad`s regime in Syria and at replacing it with a just Islamic state," it said in a statement.
The statement was published after a rebel spokesman, Abu Firas, announced on Facebook "the complete merger of the major military factions fighting in Syria".
Among the groups joining the merger are Aleppo`s biggest fighting force Liwa al-Tawhid, the Salafist Ahrar al-Sham and the Army of Islam, which is concentrated around Damascus.
The Kurdish Islamic Front also joined the front.
The creation of the joint force follows major regime advances on key battlegrounds around Damascus and Aleppo in northern Syria.
Opposition sources and experts have attributed the regime`s successes in part to rebel disunity.
While Islamist rebels from different groupings have in the past formed alliances, today`s was the first merger.
The announcement came days after the death of Liwa al-Tawhid`s charismatic military chief Abdel Qader Saleh, who had reportedly made calls for unity.
All the groups are Islamist and merged "under the banner of `There is no god but God, and Mohammed is his prophet`", said Abu Firas of Liwa al-Tawhid, citing the Islamic profession of faith.
Speaking to a news agency over the Internet, Abu Firas said "the doors are open to all the military factions, and a committee is working to study the entrance of all groups that also want to join" the merger.
"It has been decided that all the factions` military, media, humanitarian and administrative offices will merge over a transitional period of three months," he added.
News of the merger came as anti-Assad protesters in Syria took to the streets for their weekly demonstrations, this time under the rallying cry "The blood of the martyr (Abdel Qader Saleh) unites us".
Saleh died from his wounds Monday, after an air strike hit the building in Aleppo where he and other faction leaders were meeting days earlier.
Activists on the ground welcomed the merger as "bad news" both for Assad`s regime and for the jihadist Islamic State of Iraq and the Levant, which has fought against some rebel brigades in opposition-held areas.
"The news will terrorise the regime and ISIL at the same time," said an activist group.