Russian President Vladimir Putin has said his Iranian and Turkish counterparts have supported a proposal to hold a "Syrian people's congress" that will bring together government and opposition figures.

The Russian leader on Wednesday hosted Hassan Rouhani and Recep Tayyip Erdogan, just as some Syrian opposition groups met in Saudi Arabiainfo-icon's capital, Riyadh, ahead of United Nationsinfo-icon-sponsored talks in Geneva. 

"The congress will look at the key questions on Syriainfo-icon's national agenda," Putin told reporters at the summit  in the Black Sea resort of Sochi, sitting alongside Rouhani and Erdogan.

"First of all, that is the drawing-up of a framework for the future structure of the state, the adoption of a new constitution, and, on the basis of that, the holding of electionsinfo-icon under United Nations supervision."

The congress is expected to also take place in Sochi ahead of the next round of Geneva talks on November 28. However, no details about the exact date or who will be invited to attend were released.

In a joint statement, the three leaders underlined the need for all warring sides to release all prisoners and hostages, hand over bodies and create the conditions for a lasting truce.

They also urged the international community to provide humanitarian aid, clear Syrian territory of mines and restore infrastructure wrecked by the long-running conflictinfo-icon.

The leaders also discussed ways to advance a political settlement in Syria as the militant Islamic Stateinfo-icon (IS) group is nearing its defeat, while disparate Syrian opposition groups met in Saudi Arabia in a bid to form a united front for Syrian peace talks in Geneva.

"Militants in Syria have received a decisive blow, and there is a real chance to put an end to the civil warinfo-icon that has raged for many years," Russian President Vladimir Putin said at the start of talks with Turkish and Iranian counterparts in the Russian Black Sea resort of Sochi.

Putin noted that political settlement will require concessions from all sides, including Syrian President Bashar Assad's government.

Assad made a surprise trip to Russiainfo-icon late Monday for talks with Putin, which the Kremlin said were intended to lay the groundwork for the trilateral meeting Wednesday in Sochi.

Speaking after the three-way talks, Putin said that the Syrian leader pledged to conduct constitutional reforms and hold new elections under UN supervision.

In their joint statement after the talks, Putin, Iranian President Hassan Rouhani and Turkish President Recep Tayyip Erdogan emphasised the need for all parties in the Syrian conflict to release all prisoners and hostages, hand over bodies and search for those missing to help create conditions for lasting cease-fire and the launch of political talks.

"We have reached a consensus on helping the transition to an inclusive, free, fair and transparent political process that will be carried out under the leadership and ownership of the Syrian people," Erdogan said.

Even though Russia and Iraninfo-icon have backed Assad's government since the start of the Syrian conflict in March 2011, while Turkeyinfo-icon has supported his foes, the three countries have teamed up to help mediate a peace settlement.

Meanwhile, the UN envoy for Syria, Staffan de Mistura spoke at the opening of a three-day gathering of the Syrian opposition in Riyadh, where various opposition groups are expected to come up with a unified delegation and a vision for the Nov. 28 Geneva talks.

De Mistura said he planned to have two rounds of talks in Geneva in December.

"It is our common interest that today, you elect the best and most inclusive team among yourselves," de Mistura said.

The Riyadh meeting, however, has already been marred with disagreements. The notoriously fragmented opposition is divided by visions of a future role for the incumbent Syrian President Bashar Assad, the length of a transitional period as well as the constitution that will see the country move toward elections.

Around 30 various opposition delegations are attending the meeting.