Syria's main opposition group took the country's seat at the Arab League for the first time on Tuesday as the 22-member bloc opened a summit in the Qatari capital Doha.
The move that has been slammed by a furious Damascus stands as a major political gain for the opponents of President Bashar al-Assad despite their rifts.
A round of applause welcomed the Syrian rebel opposition delegation as the newcomers entered the hall after Qatar Emir Sheikh Hamad bin Khalifa Al-Thani opened the summit with a call on opposition leaders to join the meeting.
The rebel flag replaced the official Syrian one as Ahmed Moaz al-Khatib, who has resigned as the head of the National Coalition but said he would address the summit, took the seat of the head of the delegation at the gathering.
Khatib headed a delegation that included the country's first rebel prime minister, Ghassan Hitto, as well as other leaders of the opposition.
The Qatari hosts, the most vocal supporters of the revolt against President Bashar al-Assad, had won the promotion of Syria's opposition National Coalition to fill Syrian position.
The seat has been empty since the Arab League suspended Syria's membership in November 2011 after Damascus rejected an Arab proposal to end violence against protesters and instead pressed a bloody crackdown on dissent.
The Arab Spring-inspired protests morphed into an armed rebellion against Assad's regime and later into a civil war in which more than 70,000 people have been killed so far, according to UN figures.
The decision to hand the seat to the opposition has not been without its detractors, with reservations expressed by Iraq, Algeria and Lebanon.
Damascus reacted furiously to the decision of the 22-member grouping.
"The League has handed Syria's stolen seat to bandits and thugs," Syrian official daily Al-Thawra said on Monday.
"They have forgotten that it is the people who grant the powers and not the emirs of obscurantism and sand," it said, a clear reference to Qatar and Saudi Arabia.
State television station said: "Qatar wants to bypass the rules of the Arab League by giving the seat of a founding member of the League to a coalition that obeys only the money and fuel of the Gulf and submits to American dictates."
Confusing the situation, Khatib on Sunday announced his resignation, throwing the fragmented opposition into disarray and denting its credibility.
The coalition has not yet accepted Khatib's resignation.
The Arab League on March 6 called on the coalition "to form an executive body to take up Syria's seat" and attend the summit.
An opposition source told AFP that Khatib had accused "certain countries, notably Qatar, of wanting to control the opposition" and of having imposed Hitto as premier.
Khatib was accusing Qatar of having imposed the election of Hitto against Saudi-backed candidate Imad Mustafa, another opposition source said.
Apart from the Syrian crisis, Arab leaders are expected to discuss the stalled Israeli-Palestinian peace process based on a 2002 initiative offering normal relations with the Jewish state in return for its pullout from occupied land.