Syrian and Russian fighter jets carried out more than 20 airstrikes in towns near Idlib on Tuesday, ahead of an expected government offensive designed to drive out the rebels who control the Syrian city, NBC News reported.
It was the first time in more than three weeks that Russia was involved in airstrikes in the Idlib area, according to the the Syrian Observatory for Human Rights, a U.K.-based monitoring group.
Four people were killed in strikes in and around Jisr al-Shughur, according to activist Hadi Khrat. The town is located 30 miles southwest of Idlib.
The airstrikes came hours after President Donald Trump warned Syrian President Bashar al-Assad not to "recklessly attack" the area.
"The Russians and Iranians would be making a grave humanitarian mistake to take part in this potential human tragedy. Hundreds of thousands of people could be killed. Don’t let that happen!" Trump tweeted late Monday.
Idlib is the country's last remaining rebel-held enclave. Nearly 3 million civilians live there — including many refugees from other war-torn parts of Syria. However, thousands of its residents are believed to belong to powerful extremist groups, prompting fears that civilians will be caught up in the violence.