Syrian opposition figures who reject foreign intervention in the country's 18-month conflict have called for the removal of President Bashar al-Assad at a rare meeting in the nation's capital.
Sunday's opposition conference was attended by diplomats from Iran, Russia and China, Assad's main international allies.
The loose network of Syrian rebel groups and the political opposition outside Syria believe Assad will not carry out reforms or a peaceful transfer of power, and some have called for foreign military intervention to break the stalemate in the conflict.
The United States and its allies have refrained from such action, partly because of international divisions over Syria and fears of a wider conflict.
The opposition figures who met in Damascus said they were open to the idea of a political settlement, even though the conflict so far has eluded all attempts at mediation.
Tight security around Damascus
Assad's government tightly restricts criticism in areas it controls, and security was tight for Sunday's one-day conference at a Damascus hotel, attended by dozens of people. Streets leading to the hotel were blocked off, plainclothes security agents patrolled the perimeter and participants passed through security checks.
A bomb hidden in a black bag exploded on a footbridge in downtown Damascus, close to the Four Seasons hotel, about a kilometre from where Sunday's opposition conference was held.
Two people suffered slight injuries, witnesses said.
Sunday's meeting was organised by the National Coordination Body for Democratic Change in Syria, or NCB, an umbrella for 16 opposition groups.
On Thursday, two senior NCB leaders disappeared after landing at Damascus International Airport, along with a friend who was to pick them up, and the NCB has blamed the government for the disappearance.
The government claimed the three were kidnapped by "terrorist groups", a phrase it uses to describe rebels.
Despite the incident, the group said participants agreed on the idea of "overthrowing the regime with all its symbols" while emphasising the need for "peaceful struggle to achieve the goals of the revolution".
"It's our right to meet here in the capital to express our views without being subject to dictates and pressures or to be forced to make concessions," said Hassan Abdul-Azim, the NCB's head, who spent years in Syrian prisons for his role as an opposition leader.
The strong language may be aimed at gaining credibility among Syrians who do not support the government, but are also weary of a conflict that has descended into civil war in many areas.
NCB leaders, most of them traditional leftists, accuse the rebels and the Syrian National Council, a political opposition group based outside Syria, of being beholden to Turkey, which shelters defected Syrian generals and opposition figures, as well as Gulf Arab countries that support the rebels.
The rebels, in turn, accuse the NCB of being cut off from grassroots opposition fighters on the ground. Many rebels look askance at any political plan short of Assad's immediate removal, seeing it as a play for time.
The statement emerging from Sunday's conference called for an immediate ceasefire accompanied by the full withdrawal of the Syrian army from towns and cities and the release of all political detainees and kidnapped people.
This would be followed by the start of negotiations between the opposition and representatives of the Syrian government on a peaceful transition of power, it added.
The scenario outlined by the participants is similar to a six-point peace plan proposed by Kofi Annan, the former international peace envoy to Syria.
Azmat Allah Kolmahmedov, the Russian ambassador in Damascus, praised the conference, calling it a "direct implementation of the process of reforms launched by the Syrian government, including the freedom of expression."
Opposition bases hit
Meanwhile, government aircraft bombed opposition bastions nationwide on Sunday as rebels said they now controlled most of the country and had moved their command centre from Turkey to "liberated areas" inside Syria.
At least 40 people were killed, the Syrian Observatory for Human Rights said, as aircraft carried out strikes in central Homs province, Deir Ezzor in the east and areas of Damascus.
Apartment blocks in Albu Kamal, a town in oil-rich Deir Ezzor province, were targeted as rebels and soldiers battled on the ground in several districts of the town on the Iraqi border.
"The insurgents are trying to wrest control of this strategic town," said Observatory chief Rami Abdel Rahman. Losing Albu Kamal would be "a deadly blow for the regime", he added.
Helicopter gunships opened fire on the Damascus neighbourhoods of Barzeh and Qaboon as well as the suburb of Harasta, while troops pounded rebel areas in Aleppo in the north and neighbouring Idlib and Deraa in the south, the Observatory reported.
As the fighting continued unabated, Colonel Ahmad Abdul Wahab of the Free Syrian Army said the regime's aerial superiority was the only thing preventing the FSA from taking control of the capital.
"We control most of the country. In most regions, the soldiers are prisoners of their barracks. They go out very little and we can move freely everywhere, except Damascus," Abdul Wahab said.
"With or without outside help, the fall of the regime is a question of months, not years," he said.
"If we had anti-aircraft and anti-tank missiles, we could quickly gain the advantage. But if foreign countries don't give us these, we will still win. It will take longer, that's all."