Rebels won Syria's long-vacant seat at the Arab League on Monday, on the eve of the organisation's annual summit in Doha, despite rifts within the opposition that have marred their political gains.
Away from the politics, rebel Free Syrian Army commander Riad al-Asaad was wounded in a blast that hit his car in the east of the country, the Syrian Observatory for Human Rights said.
A government official in Ankara said Asaad had lost a leg in the attack on Sunday night but was in "good condition" after being rushed across the Syrian border into Turkey for treatment.
The opposition National Coalition, meanwhile, "has been invited to the Arab summit and will occupy Syria's seat" at the 22-member Arab League, a high-ranking League official in the Qatari capital told AFP.
Damascus reacted with fury to the announcement.
"The League has handed Syria's stolen seat to bandits and thugs," Syrian government daily Al-Thawra said.
"They have forgotten that it is the people who grant the powers and not the emirs of obscurantism and sand," it said, in an apparent allusion to key opposition supporters Qatar and Saudi Arabia.
A 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."
The news came a day after National Coalition leader Ahmed Moaz al-Khatib announced his resignation, throwing the fragmented opposition into disarray and denting its credibility.
However, Khatib said he will address the summit "in the name of the Syrian people," while the Coalition's envoy to Doha, Nizar al-Haraki, told AFP that Khatib will head the delegation representing Syria on Tuesday.
"I have decided to make a speech in the name of the Syrian people at the Doha summit," Khatib announced in a statement on his Facebook page, saying he took his decision after prayers and consulting friends.
"This is not linked to the resignation which will be later discussed," he added.
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The Coalition has said it refused Khatib's resignation.
Haraki told AFP that Khatib will "head the eight-member Syrian delegation at the summit and will occupy Syria's seat." The delegation will include Syria's first rebel prime minister, Ghassan Hitto.
In Washington, officials said Khatib's resignation was regrettable but would not affect Washington's support for the rebels.
"We're sorry to see him go," White House deputy press secretary Josh Earnest told reporters. But "Khatib's announcement does not change the US policy of support for the Syrian opposition and the Syrian opposition coalition.
"And the opposition to brutal rule is bigger than one person, and that movement will continue," he said.
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, although Iraq and Algeria have expressed reservations, while Lebanon has distanced itself from the decision.
The League in November 2011 suspended Syria after Damascus failed to implement an Arab deal designed to end violence against protesters.
The move came after President Bashar al-Assad's regime launched a bloody crackdown on dissent which has since morphed into a civil war in which more than 70,000 people have been killed, according to UN figures.
National Coalition member Ahmed Ramadan said Khatib has come under "intense pressure from Arab foreign ministers and from within the Coalition to reconsider his decision."
Key opposition backer Qatar has also urged Khatib to reverse his decision, which came just days after Hitto's election in Istanbul.
An opposition source told AFP that Khatib has accused "certain countries, notably Qatar, of wanting to control the opposition" and of having imposed Hitto as premier.
Back on the battlefront, a civilian plane was hit by anti-aircraft fire on Monday as it overflew the Idlib region of northwest Syria, the Observatory said, without giving details on its fate.
A UN spokesman, meanwhile, said the United Nations is removing about half of its 100 international staffers posted in Syria as attacks edge closer to the buildings of the world body.
Mortar rounds have fallen on the Damascus hotel used by UN workers, according to UN spokesman Martin Nesirky.