The Syrian regime has intensified its airstrikes against the northwestern Idlib province in the past ten days, said the Syrian Observatory for Human Rights Tuesday. The “White Helmets” rescue organization that operates in opposition areas of Syria said five people were killed by shelling and airstrikes on Tuesday, including three children. According to a senior data analyst at Hala Systems, which operates an early warning system for aerial bombardment called Sentry, 13 strikes had been observed in Idlib and northern Hama on Tuesday. “This is the third straight day in which a significant increase in airstrikes has been observed. The pace of attacks seems high — and certainly unusual compared to the last few months,” the analyst, who declined to be identified, told Reuters. “The bombing is focused mainly on towns along the Damascus-Aleppo international road,” said Observatory Director Rami Abdulrahman. The strikes against the last opposition bastion has forced thousands to flee the town of Khan Sheikhoun. “Khan Sheikhoun has turned into a ghost town,” said Abdulrahman. The area near the Turkish frontier is under a ceasefire brokered last year by regime ally Russia, and Turkey, one of the main supporters of opposition factions that have fought to topple him for eight years. Hundreds of thousands of people who fled other parts of Syria are sheltering in the enclave, protected by the truce which was aimed at averting an all-out regime assault. Any suggestion that the ceasefire is under new strain is closely watched by the warring parties and their allies. Under the agreement brokered by Russia and Turkey, the enclave in the northwest includes a demilitarized zone that must be kept free of all heavy weapons and extremist fighters. Moscow has complained about escalating violence in Idlib and said that militants who used to belong to the Nusra Front, Syria’s former chapter of al-Qaeda, are in control of large swathes of territory. Twenty regime troops and allied fighters were killed in attacks by an extremist group on the edge of Idlib since Sunday, the Observatory said. The latest casualties were five regime and allied fighters killed Tuesday near the planned buffer zone. The Observatory said the attack was led by Hurras al-Deen, an alliance formally linked to al-Qaeda that includes Syrian and foreign extremists. At least nine militants were killed in the clashes, among the deadliest since the ceasefire deal was reached in September. Syria’s conflict began in 2011 after Bashar Assad’s security forces used force to crush mass demonstrations against his rule. Hundreds of thousands of people have been killed and millions displaced in the conflict, which has drawn in world powers.