"Russia, Syria, and Iran are killing, or on their way to killing, thousands of innocent civil in Idlib Province. Don't do it!" Trump tweeted on Thursday.
Trump added in his tweet that "Turkey is working hard to stop this carnage," without providing further details, Xinhua reported.
Forces loyal to the Syrian government, backed by Russian airstrikes, have launched a fresh round of fierce offensives in Idlib to capture the last rebels' stronghold in the war-torn country.
The Syrian army said in a statement on Tuesday that it will continue the military operation until "liberating" Idlib Province from "terrorists," state news agency SANA reported.
The statement urged civil in Idlib to stay away from the rebel positions, noting that the army will "liberate" Idlib while preserving the lives of the civil.
About 110,000 civil have so far fled their homes in the southern countryside of Syria's Idlib Province as a result of a military showdown there, a war monitor reported Thursday.
Turkish presidential spokesperson Ibrahim Kalin said Tuesday evening that Ankara asked Moscow to establish a cease-fire in Idlib after the region has seen an uptick of violence in recent days.
Turkey and Russia agreed in September 2018 to turn parts of Idlib into a de-escalation zone in which acts of aggression are prohibited.
However, such deals exclude the ultra-radical rebels who are affiliated with the al-Qaida and branded as terrorist groups by the UN.
Idlib hosts some 3 million people including many displaced by years of violence in other parts of Syria.
( With inputs from IANS )