He added: "The Russians and Iranians would be making a grave humanitarian mistake to take part in this potential human tragedy".
The Britain-based monitor, which relies on sources in Syria for its reports, said at least nine civilians, including five children from the same family, were killed in the raids, while 10 people were wounded. "Don't let that happen!"
Russian media outlet the Moscow Times says a large-scale naval exercise now underway in the eastern Mediterranean "coincides with rising tensions between Moscow and Washington over Syria".
He also called on two major backers of President Bashar al-Assad's military to also restrain their actions.
USA officials, meanwhile, have been working behind the scenes to delay an attack.
The Mazzeh airbase houses Syrian Air Force intelligence, and in early 2017 the Syrian government accused its neighbour Israel of bombing the base.
But analysts still say the United States appears resigned to the likelihood of a final military victory by Syrian regime forces. Despite the accounts of witnesses, the Syrian government denied involvement in the attack.
Judge orders USA couple to hand crowdfunding money over to homeless veteran
During an appearance on United States television on Monday, D'Amico revealed there is well over $150,000 left of the donations. The couple has been accused of misappropriating funds and ordered by a judge to give the money to Bobbitt .
An Israeli military official said Tuesday that Israel has struck over 200 Iranian targets in Syria over the past 18 months.
Zarif left early on Monday and "is at the moment in talks with Syrian officials", spokesman Bahram Ghasemi told reporters in Tehran.
The Kremlin on Tuesday dismissed his comments, describing Idlib, where jihadist insurgent factions dominate, as a "nest of terrorism". "And the remaining terrorists in the remaining parts of Idlib must be cleaned out and the region should be placed back under the control of the Syrian people".
About 6.2 million Syrians have been displaced since the conflict began in 2011, with a further 6.3 million having fled overseas as refugees, according to a recent UNHCR report.
The United Nations and aid groups have warned that a full assault on Idlib could spark a humanitarian catastrophe on a scale not yet seen in Syria's seven-year-old conflict.
An opposition source and the Observatory both said the air strikes were in the countryside near Jisr al-Shughour on the western edge of the opposition's northwestern territory.
Trump blasts book's claims that he called Sessions 'a dumb southerner'
Trump insisted he "never used those terms on anyone, including Jeff", adding that "being a southerner is a GREAT thing". While aides described his tweets as the "devil's workshop", Trump has insisted he was the Ernest Hemingway of Twitter.
Idlib and the surrounding area is home to some three million people - almost half of them already displaced a few times by the civil war.
Other examples of Trump setting red lines for Syria?
Meanwhile, Tehran based Press TV reports from Beirut that Sheikh Naim Qassem, Deputy Secretary General of Hezbollah has said that U.S., whose pro-terror policies have faced defeat in Syria, is in no position to call for the withdrawal of Iranian advisors and allied Lebanese resistance fighters, who have emerged as "victors" of the war against terrorists in Syria.
Idlib hosts a ragtag group of rebels, including Chechen and Chinese Uyghur fighters.
Any offensive on Idlib could raise tensions with Turkey, which maintains observation posts around rebel territory as part of a "de-escalation deal" with Russian Federation and Iran.
"There's no good solution to this".
Eagles quarterback Carson Wentz not yet cleared for contact
As a result, Pederson hasn't settled on a starter for Thursday's season opener against the Atlanta Falcons . Foles' recovery thus gives Wentz more time to recover ahead of his reintegration on the field.