Besides al-Khatib, the Syrian delegation included Ghassan Hitto, recently elected prime minister of a planned interim government to administer rebel-held areas in Syria, and two prominent opposition figures, George Sabra and Suheir Atassi.
Al-Khatib announced his resignation on Sunday because of what he described as restrictions on his work and frustration with the level of international aid for the opposition. The coalition rejected the resignation and al-Khatib said he would discuss the issue later and represent the opposition at the Qatar summit "in the name of the Syrian people."
Also, Hitto's election as the head of the interim government was rejected by the opposition's military office, which said he was not a consensus figure. Some members have accused Qatar and the Muslim Brotherhood of imposing their will on the Coalition.
Atassi briefly suspended her membership in the coalition after Hitto was elected.
Addressing the gathering, al-Khatib thanked the Arab League for granting the seat to the opposition and lamented the inaction of several foreign governments, which he did not name, toward the Syrian crisis despite the suffering of civilians in his country.
"I convey to you the greetings of the orphans, widows, the wounded, the detained and the homeless," al-Khatib told the gathering in an opulent hall in Doha.
Most of the mortar strikes hit the capital's east side, falling near a school in the Baramkeh neighborhood, the Damascus Hospital, the Law Faculty of Damascus University and the state news agency's own offices.
SANA said one girl and two other civilians were killed.
A government official in Damascus told The Associated Press that four people were killed and 42 wounded. The official spoke on condition of anonymity because he was not authorized to brief the media, and the discrepancy could not immediately be resolved.
Mortar rounds also fell in a number of areas on the city's west side, including the Christian neighborhood of Bab Touma, SANA said.
The agency published photos of a hole in a wall of what appeared to be a school, medics treating blood-stained patients and firemen extinguishing burning cars.
It was not immediately known who fired the mortar shells. Such attacks in the capital have grown more common in recent weeks as rebels have clashed with government troops on the city's east and south sides. While the shelling rarely causes many casualties, it has shattered the aura of normalcy the regime has tried to cultivate in Damascus.
"They think that that through this tactic they can pressure residents to rise up against authorities," said Fayez Sayegh, a member of parliament and a member of the ruling Baath Party. "But on the contrary, this indiscriminate shelling makes people realize that this opposition is nothing but gangs of criminal terrorists."
Meanwhile, anti-regime activists said Syrian troops seized control of a neighborhood in the central city of Homs that is considered a symbol of opposition to Assad's regime.
The Syrian military's recapture of Baba Amr, in Homs, while not strategically important in the civil war, is a symbolic blow to the rebels. The poor, predominantly Sunni neighborhood emerged early in the uprising as a symbol of the rebel movement, first for its protests and later for the armed groups who held it against the regime onslaught.
The seesaw fight for the Homs neighborhood reflects the back-and-forth nature of Syria's civil war. While rebels appear to be gaining ground, their progress is slow and their fighters remain vulnerable to Assad's military superiority.
In other violence Tuesday, the Observatory said that at least 13 charred bodies, including four children and five women, were found on the outskirts of the village of Abil, southwest of Homs city. It said local activists blamed the killings on pro-government gunmen.
The Syrian government does not respond to requests for comment and did not mention the killing in official media.