The news came as Turkey said a major summit would take place in weeks with Russia, France and Germany
September saw lowest civilian casualty of Syrian war
Fewer Syrian civilians were killed by war-related violence in September than in any month of the seven-year war, data released on Tuesday shows.
A monitoring group that continues to keep a tally of those killed said just 139 civilians, including 58 children, were killed last month.
Of the 1,059 people who died last month, 436 were rebel fighters, 239 soldiers and allied militiamen, and 236 were from extremist groups, the Syrian Observatory for Human Rights said. The identity of nine others was unknown.
The news comes as Turkish President Tayyip Erdogan told members of his party on Tuesday that a major summit bringing together Turkey, Russia, Germany and France to discuss the future of Syria will take place in the coming weeks.
The results come after a Turkish-Russian deal to avert a regime led offensive on Idlib province in the northeast. Nearly 3 million people now live in the area and the offensive threatened to cause mass casualties and widespread displacement.
The province of Idlib is home to the last major rebel bastion in the country and aid groups had feared a full-blown regime offensive would spark suffering on a scale not yet seen since the start of the war.
The decline in the number of civilian casualties comes after months of Russian-backed government operations that saw Damascus reconquer significant territory.
Fighting is ongoing in eastern Syria, where holdout extremist fighters from ISIS are defending their last pocket in the country.
The Britain-based Observatory relies on an extensive network of sources across Syria, where it says close to 365,000 people have been killed since the start of the war.
More than 110,000 of them are civilians, it says.
The highest monthly number of civilian deaths the Observatory ever recorded was 6,657 in May 2015.
Mr Erdogan said that his military is working to bolster Turkish observation posts in Syria's northeastern Idlib province and that he will coordinate with Russia against hardline and extremist groups.
Turkey has a number of watchtowers across Idlib province as part of a deal with Russia and Iran last year to designate the region and parts of neighbouring areas a "de-escalation zone".
Speaking to members of his AK Party in parliament, Mr Erdogan said he will continue to seek a solution with the Syrian people, not the Russian-backed Syrian government, indicating its ongoing support for rebel groups would continue.
Meanwhile on Monday US Defence Secretary Jim Mattis said the United States and Turkey have started training together to carry out joint patrols soon in northern Syria's Manbij area.
The move comes even as relations between Washington and Ankara have soured in recent months over a number of issues, including Turkey's potential purchase of a Russian air-defense system.
Manbij, once in the hands of ISIS, is now held by a US-backed alliance dominated by the Kurdish People's Protection Units (YPG).
Ankara considers the YPG "terrorists" and had previously threatened to attack the city.
US support for the YPG has strained relations with Turkey, which fears the emergence of an autonomous Kurdish region on its southern border.
Under an agreement with the United States to reduce tensions, Turkey started military patrols around Manbij in June, while the US conducted its own patrols.
Now troops from both countries are training together in Turkey to conduct joint patrols, US Army spokesman Colonel Sean Ryan said.
"Right now, they are still operating independent, coordinated patrols but they are also starting...the joint training," Ryan told Pentagon reporters.