President Bashar al-Assad's forces have been amassing along Idlib's borders for weeks and shelling rebel-held territory on a daily basis, according to the Britain-based Syrian Observatory for Human Rights.
Israel has previously acknowledged having carried out air strikes in Syria aimed at degrading the capacity of Iran and its allies, including Lebanon's Shi'ite Hezbollah group, which are backing Assad in the country's seven-year civil war.
Russian air raids ceased in and around Idlib on August 15, but pro-regime forces have maintained an aerial bombardment and shelling there, the war monitor said.
The leaders of Iran, Turkey, and Russian Federation are expected to meet in Iran this week to discuss the situation in Syria.
US President Donald Trump warned President al-Assad, as well as his Russian and Iranian allies, not to attack Idlib province, citing via a Twitter post Monday evening his fears of a "grave humanitarian mistake".
The airstrikes targeted 10 areas in Idlib, the last major rebel stronghold in Syria.
But Moscow on September 4 rejected the warning, with Kremlin spokesman Dmitry Peskov saying Trump's tweet demonstrated a limited approach toward the situation in Idlib Province.
But Syrian government forces are now massing around the province, which has become the last rebel bastion in the country. "Don't let that happen!"
Asked about Mr Trump's tweet, Mr Peskov said such warnings do not take into account "the unsafe and negative potential" of the rebel-held enclave and show that the White House does not have a "comprehensive approach" to solving the Syria crisis.
The President's warning comes just days after Secretary of State Mike Pompeo issued a similar warning to Russia's foreign minister, Sergey Lavrov, saying an attack on Idlib was something that Syria and Russian Federation "agreed not to permit", and that the U.S. "sees this as an escalation of an already unsafe conflict".
Almost 3 million civilians live thre - including many refugees from other war-torn parts of Syria. Russia, like the Syrian government, refers to all opposition Syrian forces as terrorists.
The Iranian foreign minister further welcomed the decision to stage the Rebuild Syria Exhibition later in October and described it as a sign of "strong determination" to reconstruct the war-torn country.
A statement from Mr Assad's office said Iran and Syria "had similar views on the different issues" to be discussed.
Russian warplanes have been hitting targets at many civilian residential areas and the frontlines of the opposition in Syria's northwestern Idlib province. Others, obviously the families of the the militants opted to move to Idlib under the agreement.