Lebanese residents in areas north of the capital, Beirut, reported hearing jets overhead before sunset.
A Syrian government minister said the siege of Idlib would probably be resolved by force. After the latter strike, the Syrian military warned Tel Aviv of repercussions for the "flagrant attack". The attack killed a top military scientist.
However, UN envoy to Syria Staffan de Mistura has warned of a "perfect storm" if the government goes ahead with its threatened offensive.
The aftermath of an airstrike near Jisr a-Shughour on Tuesday. Russians mediated for safe transportation to their new destination. Those strikes were likely carried out by the Syrian government or its allies, which are preparing for a major offensive.
"A convoy of Iranian forces and allied militia was hit by air strikes as it drove near Al-Tanf base", the head of the monitoring group Rami Abdel Rahman said. The Observatory said 13 people were killed.
Zarif paid a day-long visit to Damascus on Monday and held talks with the country's senior officials, including President Bashar al-Assad, Foreign Minister Walid al-Muallem and Prime Minister Imad Khamis, as Syria is preparing for an operation to liberate Idlib Province, the last major militant stronghold.
Mr Pompeo retweeted the USA president's remarks about Idlib.
Speaking at the meeting with the Syrian premier on Monday, Zarif hailed recent victories of the resistance forces against foreign-backed terrorists and said following the victories, the Syrian people and government will move toward their country's reconstruction. The warning came as Russian Federation begins war games with the largest fleet it has assembled in the Mediterranean for decades while issuing pre-emptive warnings that Syrian rebels are preparing to gas themselves in a bid to spark worldwide outrage.
President Recep Tayyip Erdoğan will travel to Tehran for a trilateral meeting with his Iranian and Russian counterparts on Friday.
There are 2.9 million people presently in Idlib, according to United Nations estimates, including 1.4 million who have been displaced from their homes by fighting.
Syrian writer Leila Al-Shami wrote that "regime troops have massed on Idlib's border and leaflets have been dropped on residential areas calling on Syrians to accept "reconciliation" or face the consequences".
It also said talks were under way to establish a humanitarian corridor for civilians to leave Idlib.
The US, with Britain and France, unleashed a missile barrage against Syrian facilities earlier this year after chemical weapons were used against civilian and rebel forces.
The U.S. has twice struck Syrian military installations in response to alleged poison gas attacks.
CNN reported Friday that USA intelligence and military targeting experts have created a list of Syrian chemical weapons facilities that could be struck if Trump chose to order a new round of airstrikes in the country.
The Red Crescent, like other aid organisations in Turkey, was "taking necessary measures in this regard, whether within Syria or within Turkey", he said.
In May, it said it attacked almost all of Iran's military infrastructure in Syria after Iranian forces fired rockets at Israeli-held territory for the first time in the most extensive military exchange ever between the two adversaries.
"The humanitarian crisis that could be here is different", he told reporters on his plane accompanying him to Pakistan and India.