Meanwhile, Turkish and American military officials began a two-day set of talks in the Turkish capital, Ankara, about establishing a safe zone in northeastern Syria to address Ankara's concerns about U.S.-allied Syrian Kurdish-led forces in that region.
The Syrian military said in a statement carried by state media that insurgents in Idlib had continued to break the cease fire since it went into effect late Aug. 1. State media and opposition activists had reported repeated violations of the truce by both sides since then.
The military statement said the rebels also failed to abide by an agreement reached last year to withdraw from a demilitarized zone surrounding the enclave. The cease fire marked a brief pause in the stalled government offensive against al-Qaida-linked militants and other jihadi groups, which dominate Idlib and surrounding areas.
The assault on the rebel stronghold began April 30, displacing more than 400,000 people and killing hundreds. Around 3 million people are living inside the rebel-held area. After the army announced it was restarting military operations, the Britain-based Syrian Observatory for Human Rights, an opposition war monitor, said Syrian and Russian warplanes began airstrikes on the southern parts of Idlib, mainly the town of Khan Sheikhoun.
The Syrian military later reported that insurgents had fired rockets at the Russian air base of Hmeimeem in Latakia province on the Mediterranean coast, "inflicting large human and material" losses outside the base. The Russian defense ministry later said three unguided rockets were fired at the base but hit a nearby village instead, injuring four civilians.
Turkey's defense minister tweeted that a new round of talks had begun with the U.S. military about creating a Turkish-controlled safe zone inside Syria east of the Euphrates River, which would have no Syrian Kurdish forces within 19-25 miles of the border. Turkey sees the Syrian Kurdish fighters as terrorists aligned with a Kurdish insurgency within Turkey.
American troops are stationed in northeastern Syria along with the Kurdish forces, and have fought the Islamic State group together. Turkish-U.S. negotiations on the safe zone stalled in recent weeks, and Turkish President Recep Tayyip Erdogan has repeatedly threatened a new military operation into the area. On Sunday, Erdogan renewed that threat.
For their part, the Syrian Kurds say Ankara's statements mask a territorial grab inside Syria, which the Kurdish forces had liberated from IS militants. The Syrian Democratic Council issued a statement Monday saying that its military wing — the U.S.-backed and Kurdish-led Syrian Democratic Forces — is a "force to defend" Syria's ethnic and cultural pluralism.
The council added that Ankara "is trying to deceive the public" and to get the U.S. and other parties to "participate in the crimes that Turkey is committing against humanity."