Islamist fighters have seized 17 checkpoints from Syrian forces in clashes around the city of Idlib that have cost at least 71 lives, a monitor said Thursday.
"The government and its supporting forces have lost 17 checkpoints and regime locations to the Al-Nusra Front and other Islamist groups in and around Idlib" in the country's northwest, said the Syrian Observatory for Human Rights.
The clashes come as part of an Islamist offensive launched Tuesday and led by Al-Qaeda affiliate, the Al-Nusra Front, on the regime-held city of Idlib.
Calling itself "The Army of Conquest," the new Islamist coalition said on Twitter Tuesday that it was preparing for "the invasion of Idlib" in order "to liberate this good city."
Citing eyewitnesses, the Observatory said heavy shelling by the Islamist fighters had forced "regime forces to erect new checkpoints and barricades" in the city.
"The violent clashes are ongoing for a third continuous day, and the regime and (pro-government militia) National Defence Forces are trying to regain the initiative despite the severity of the offensive," the Observatory said.
Idlib province is largely under the control of Al-Nusra, but provincial capital Idlib city remains in regime hands.
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It would be only the second provincial capital lost by the regime after Raqa, which is now the de facto capital of the Islamic State group.
Since Tuesday, the clashes have left at least 37 Islamist militants and 34 fighters from pro-regime forces dead, the Britain-based Observatory said.
Among those killed was Abu Jamil al-Qutb, the second-in-command of Ahrar al-Sham, one of the first armed groups in Syria's conflict and a major part of the new "Army of Conquest" coalition.
Ahrar al-Sham published a video Thursday addressed to "our people and the mujahedeen in the city of Idlib."
In it, the group's religious guide Abu Mohammad al-Sadeq called on fighters to join them and for residents to stay indoors during the offensive.
Government forces also control the Idlib towns of Jisr al-Shughur and Ariha, Abu Duhur military airport and five military bases in the province.
Meanwhile, in the southern province of Daraa, at least 22 people, including four children, were killed in regime air strikes on the provincial capital, the Observatory reported.
More than 215,000 people have been killed in Syria's four-year conflict and around half the country's population has been displaced.