Members of Syria's internal opposition held a rare meeting in Damascus to call for a peaceful end to President Bashar al-Assad's rule, after months of fighting in which thousands have been killed.

The meeting went ahead with the blessing of authorities despite the arrest of several opposition figures in recent days.

There have been accusations from rebel forces that it gave a false signal that Assad is seeking a political solution to Syria's crisis.

Rajaa Nasser, one of the organisers of the Syria Salvation Conference, called for "an immediate halt to the shooting, a halt to the brutal and barbaric shelling, a truce and a pause for the fighters."

He said such a truce could "open the way for a political process ... which guarantees a radical political change, an end to the current regime and a serious and genuine democracy." 

Activists say 27,000 people have been killed in Syria since protests against Assad erupted in March last year.

Western countries, reluctant to intervene militarily, have called for the president to step aside but their pressure for United Nations sanctions against Damascus has been blocked by Russia and China.

Russia's ambassador Azamat Kulmukhametov said; "the main goal now is to put an immediate end to the violence in Syria, whether from the government side or the armed groups," 

He said that "the other goal is no less important, to convert the current confrontation ... into a peaceful political solution."

Assad has vowed to crush rebel fighters, who he portrays as foreign-backed Islamist terrorists.

He says he accepts some opposition figures who call for a peaceful transition from a one-party state to democracy.

His allies have pointed to the internal opposition as a sign Assad is serious about reform.

Members of the internal opposition, which includes outspoken critics of Assad who have spent years in jail, said Moscow and Beijing promised to exert influence to protect today's meeting.

But eight members of the National Coordination Body were detained by Syrian security forces last week, including three who were seized outside Damascus airport after they returned from a trip to China, the group's spokesman said.

The internal opposition has been accused of being too passive by rebel fighters and members of the largely foreign-based Syrian National Council, a political group calling for the international community to arm rebel factions.

A spokesman for the rebel Free Syrian Army said; "this is not a real opposition in Syria. This opposition is just the other face of the same coin,"

"It is just a silly plot to mislead the international community to think there is a negotiation in place. They cannot be successful in finding an end to the civil war."