Syria's splintered opposition was gathering in Saudi Arabia on Tuesday for difficult discussions on forming a united front in potential peace talks with President Bashar Assad.

The Saudi-organized talks, due to start on Wednesday, mark the first time representatives of some of Syria's various political and armed opposition factions come together since the outbreak of the country's conflict in March 2011.

The U.S.-led coalition fighting the Islamic State group said Tuesday it was "assessing the credibility" of reports its strikes killed at least 26 civilians in a Syrian village on Monday.

"Every time we get information about the possibility of a civilian casualty incident, we always do a credibility assessment on that information," Colonel Steve Warren told AFP.

The powerful Jaish al-Islam rebel group announced late Monday it will attend a major meeting of Syrian opposition forces in Riyadh this week, the first rebel group to confirm participation.

In an emailed statement, Jaish al-Islam (Army of Islam) spokesman Islam Alloush said it would send two delegates, Mohammad Alloush and Mohammad Birqdar, to the conference, which is set to begin on Wednesday.

Maronite Patriarch Beshara al-Rahi returned to Lebanon from a pastoral visit to Syria on Monday, where he also discussed the presidential elections, reported al-Joumhouria on Tuesday.

It said that Syrian officials expressed to the patriarch their “reservations” over the potential nomination of Marada Movement chief MP Suleiman Franjieh as president.

Russian jets shelled on Monday the positions of gunmen on the eastern mountain range, reported the National News Agency.

It said that the sound of explosions could be heard in the border area with Syria on the outskirts of the northeastern border region of Arsal.

The departure of Syrian President Bashar Assad is no longer necessary before any political transition in the war-torn country, French Foreign Minister Laurent Fabius said in an interview published Saturday.

The comments mark a softening of Paris' position on the Syrian president as attention turns to the fight against the Islamic State group which staged a series of bloody attacks on the French capital last month, killing 130.

An Australian man who reportedly joined a group fighting Islamic State jihadists in Syria will be deported from Germany, the foreign ministry said Saturday.

Australian media had reported that Ashley Dyball was detained in Germany after traveling to Europe for a break from working with a Kurdish militia group known as YPG.

Heavy government bombardment of rebel-held towns across Syria on Friday killed at least 56 civilians, more than a quarter of them children, a monitoring group said.

The bloodiest attacks were in Eastern Ghouta, a rebel stronghold east of Damascus, where at least 41 civilians were killed, the Syrian Observatory for Human Rights said.

Interior Minister Nouhad al-Mashnouq hailed on Friday the General Security on its success in releasing the 16 servicemen who were being held by the extremist al-Nusra Front, acknowledging that the northeastern border region of Arsal is “occupied”.

He said in a press conference after meeting General Security chief Abbas Ibrahim: “The region of Arsal is occupied and our main policy is to avoid being dragged into the Syrian conflict.”

Pressure is mounting on the Netherlands to join U.S.-led air strikes against Islamic State extremists in Syria, with several lawmakers late Thursday joining calls for a bombing campaign.

The Dutch cabinet however said it will reach a decision to take part in the U.S.-led operation only once "all military and political aspects" of the Syrian conflict had been discussed.