Russia's Syria's congress aimed at bringing the country's seven-year war to an end opened on Tuesday despite boycotts by the main opposition group and Kurds, as well as rebels pulling out at the last minute.
Regime-backer Moscow has invited 1,600 delegates to the meeting in the Black Sea resort of Sochi as part of a broader push to consolidate its influence in the Middle East and start hammering out a political solution to the conflict
An opening speech by Russian Foreign Minister Sergei Lavrov, delayed by two hours because of ongoing negotiations, was interrupted both by cries of "Long live Russia!" and angry heckling from Syrian delegates.
Reading out a letter from President Vladimir Putin, Lavrov called for the UN to play a leading role in any political settlement, following fears among Western powers that Russia is seeking to undermine separate UN-backed talks with a view to carving out a deal that strengthens its ally President Bashar al-Assad.
The main aim of the talks is to establish a committee to create a post-war constitution for Syria with United Nations backing, according to a draft statement seen by AFP.
Representatives of rebel groups flew into Sochi from Turkey late Monday but refused to leave the airport after seeing the symbol of the congress featured only the Syrian regime flag, a source said.
The source told AFP that Russian hosts had promised to change the symbol, which was displayed on posters in the airport as well as billboards on the road towards Sochi, and in the congress hall itself.
Lavrov and Turkish foreign minister Mevlut Cavusoglu spoke twice on Tuesday morning in a bid to resolve the issue, Artyom Kozhin of the Russian foreign ministry said.
But after almost 12 hours of negotiations some 80 rebels, politicians and activists refused to participate in the congress and prepared to return to Turkey, said rebel Ahmad al-Saoud.
Moscow said Syrian society would be fully represented at the meeting -- the first of its kind held in Russia -- but almost all confirmed are from either Assad's ruling Baath Party, allied movements or the regime's "tolerated opposition".
The Syrian Negotiation Commission (SNC), the country's main opposition group, said following two days of UN-led talks in Vienna last week it would not attend the Sochi congress.
The SNC accused Assad and his Russian backers of continuing to rely on military might and showing no willingness to enter into honest negotiations.
Authorities from Syria's Kurdish autonomous region said at the weekend they would also boycott the event because of the ongoing Turkish offensive on the Kurdish enclave of Afrin.
Turkey, which supports Syrian rebels vying for Assad's ousting, is co-sponsoring the congress along with regime-backer Iran.
Members of the opposition and some Kurds would attend in an individual capacity, the Kremlin's special envoy on the Syria peace process Alexander Lavrentyev said earlier.
The UN's Syria peace negotiator Staffan de Mistura was at the event despite last-minute questions over whether he would attend.
The US State Department on Monday said it would not send observers to the Sochi conference, saying "our collective focus must remain on the UN-led political process".
But Mohannad Dleikan, a representative of the Syrian opposition's so-called Moscow Group, which is attending Sochi but has been accused by the mainstream opposition of toeing a more conciliatory line on Assad's future, said the aims of the talks were the same as those of the UN.
"If there is a consensus in Sochi, that will be a serious message to those in Geneva, whether it be the opposition or the regime," he told AFP from Beirut.
"We have obtained sufficient guarantees that this process will support Geneva, it will not act as an alternative."
Russia, which has spearheaded several rounds of talks from the start of last year in Kazakhstan's Astana, initially hoped to convene the congress in Sochi last November but those efforts collapsed following a lack of agreement among co-sponsors.
Moscow's decision to launch a bombing campaign to support Assad in September 2015 -- Russia's first major military operation abroad since Soviet troops withdrew from Afghanistan in 1989 -- is widely seen as a turning point in the multi-front conflict that helped shore up the Syrian president.
The Syrian war, in which more than 340,000 people have died and millions more been displaced, began in 2011 as the regime crushed anti-government protests.