Deadly attacks in France's capital have overshadowed talks in Vienna between senior officials from 19 countries that aim to chart a way towards a ceasefire and political transition in Syria to end the country's war.
As the meeting on Saturday - including Iran, Saudi Arabia, Russia, the US and Turkey - went ahead, French Foreign Minister Laurent Fabius said the attacks in Paris made it all the more necessary for the international community to find a common approach in Syria and terrorism, sentiments echoed by the foreign ministers of Germany, Jordan and Saudi Arabia.
His comments came after France declared a state of emergency and three days of mourning after coordinated attacks claimed by the Islamic State of Iraq and the Levant (ISIL) group in Paris killed at least 128 people late on Friday evening.
Also in Vienna, US Secretary of State John Kerry said: "If they've [the attacks] done anything, they've encouraged us today to do even harder work to make progress and to help resolve the crises that we face.
"These kinds of attacks are the most vile, horrendous, outrageous, unacceptable acts on the planet."
The meeting leaders must overcome deep differences to try and end the almost five-year conflict in Syria, such as decide on what, if any role Syrian President Bashar al-Assad should play in any transition government.
Russia's Foreign Minister Sergey Lavrov said there was "no justification for terrorist acts, and no justification for us not doing much more to defeat ISIS and al-Nusra and the like," referring to ISIL and the Syrian branch of al-Qaeda, the Nusra Front. "I hope that this meeting as well would allow us to move forward," he added.
The meeting comes amid new pushes against ISIL in Syria and Iraq.
More than 250,000 people have been killed in the Syrian war. Eleven million have been uprooted from their homes.
| Syrian refugees in Greece despair of peace
Europe and Syria's neighbours, meanwhile, are struggling to cope with the influx of refugees trying to escape war.
Al Jazeera's Mohammed Jamjoom, reporting from Vienna, said anti-war protesters welcomed the meeting as well as those who supported the Syrian president.
"Some were here saying the fighting must stop immediately." he said. "They were here to show their solidarity with the French people."
He added that refugees from Syria and Iraq, who he had spent time with over the past two weeks in Greece, were concerned that attacks in Europe would further harm their plight.
"They are the ones left out in the cold right now," he said.
Meanwhile in Syria, fighting has intensified since September 30 when Russian air strikes were launched for the first time in the country's war.
Russian and regime air strikes pounded Damascus suburbs in recent weeks, targeting opposition-held towns, while Syrian army forces continued to advance in southern Damascus.
In Moadamiyah, Syrian government helicopters dropped at least 100 barrel bombs on the town's residential outskirts during the first week of November, according to local residents.
"They targeted the eastern and southern parts of the city," Dani Qabbani, a media activist, told Al Jazeera.
Syrian government forces and Assad's militias "shelled us, [targeted] us with all types of weapons", he said. "Many civilians were injured. People are terrified."
Qabbani said clashes between opposition Free Syrian Army forces and fighters from Hezbollah, the Lebanese group that battles alongside the Assad government, have deepened in recent weeks.
"There are large numbers of [Hezbollah] soldiers and Assad's gangs," Qabbani added.
Last month, Lebanese media reports cited Hezbollah security officials saying they would not engage in further offensive operations in Syria after the takeover of Zabadani, a rebel-held town southwest of Damascus and the site of ongoing fighting.
Sharif Nashashibi, a London-based writer and Middle East analyst, said that he doubts Hezbollah will curb its activities in Syria.
"Hezbollah is in Syria to prop up the regime, and the regime is still in a great deal of trouble," Nashashibi told Al Jazeera."
The UK-based Syrian Observatory for Human Rights says that Moscow's first month of air strikes killed more civilians than ISIL fighters.
Russian weapons fired from Russian planes from September 30 until October 31 killed at least 185 civilians, including 46 women and 48 children, the monitor said.
Russian air strikes also killed at least 279 fighters, the monitor added.
With additional reporting by Patrick Strickland: @P_Strickland_
Source: Al Jazeera and agencies