Syria's opposition National Coalition has taken the country's official seat at the Arab League summit in Qatar.The delegation led by Ahmed Moaz al-Khatib, who has said he will resign as head of the coalition, was applauded as it formally assumed the seat.
Mr Khatib called it "part of the restoration of legitimacy" that Syrians had "long been robbed of".
The move has enraged Damascus who accused the League of handing the seat to "bandits and thugs".
The government of Bashar al-Assad was suspended by the Arab League in November 2011 in response to its crackdown on the opposition.
Meanwhile, in Syria itself, government troops are reported to have seized back control of the long-contested Baba Amr district of Homs after two weeks of fighting.
At least 13 burned bodies have been found in the village of Abel, just outside the central Syrian city, said the British-based Syrian Observatory for Human Rights, which is documenting incidents and casualties.
And Syria's state media are reporting mortar explosions in the west of the capital, Damascus, with several people wounded.
Emotional speech Syria's National Coalition was formally invited to assume the seat by the summit chair, the Emir of Qatar, as the two-day meeting opened in Doha.
Mr Khatib was joined by the opposition's recently-elected interim Prime Minister Ghassan Hitto and two other prominent opposition figures George Sabra and Suheir Atassi.
The Syrian flag was replaced at the country's official seat with the flag being used by the opposition.
Mr Khatib gave an impassioned speech in the name of the 100,000 people he said had given their lives in the struggle so far, and the many others who have been wounded, tortured or imprisoned.
He said he had asked the new US Secretary of State, John Kerry, to provide Patriot surface-to-air missiles to help protect rebel-held areas in the north of Syria from regime air strikes.
Mr Khatib rejected attempts by some outside powers to control Syrian decisions, saying the country's future would be decided by the Syrian people alone, the BBC's Jim Muir reports.
And he also rejected all the reasons advanced by western powers and others for the reluctance to provide the Syrian opposition with the means to defend the people, our correspondent adds.
The National Council's seat at the Arab League comes at a time of disarray within its top ranks.
Ahmed Moaz al-Khatib - seen as a respected and unifying figure in Syria - announced his resignation on Sunday, a move so far rejected by the coalition.
He said he had promised to resign if certain "red lines" were reached. Although he did not specify what those red lines were, he did accuse world powers of failing to adequately protect the Syrian people.
But analysts say Mr Khatib is also concerned by the influence of Islamists and foreign powers like Qatar in the opposition coalition.
And his resignation came days after US-based Islamist Ghassan Hitto was elected by the opposition to be prime minister of an alternative administration that could govern rebel-held areas from inside Syria.
Mr Khatib was against such an administration, and observers say he may have feared the move would further distance the outside opposition leadership from what is going on inside Syria.