More than 100 fighters have been killed in two days clashes between regime and extremist-led opposition forces in north-west Syria, a war monitor said, as violence raged on the edge of an opposition bastion despite a September truce deal. Eight civilians also died in the latest violence since Wednesday, the Syrian Observatory for Human Rights said. Six of them, including a child, were killed in regime air strikes on the town of Jisr Al Shughur. The UN said it had received reports that the strikes hit medical facilities and healthcare workers. Syria's civil war has killed more than 400,000 people and spiralled into a complex conflict since starting in 2011 with the repression of anti-government protests. Russian and regime aircraft have since late April ramped up the deadly bombardment of the Idlib region of about three million people in north-west Syria, despite a deal to avert a massive government assault. Regime forces have also been battling extremist militants and allied rebels on the edges of the bastion held by Syria's former Al Qaeda affiliate Hayat Tahrir Al Sham, including the north of Hama province. HTS spokesman Abu Khaled Al Shami said the group and allied rebel fighters attacked after dark, taking control of the village of Hamameyat and a hilltop. Fighting and bombardment since the launch of the attack late on Wednesday killed at least 57 regime forces and 44 opposition fighter, the Britain-based war monitor said. "The fighting is ongoing as regime planes and artillery pound the area," Observatory head Rami Abdurrahman said. UN Secretary General Antonio Guterres "strongly condemned" the air strikes and urged that "civilians and civilian infrastructure, including medical facilities, must be protected". "Several health facilities were reportedly hit yesterday, including a hospital in Maarat Al Numan, one of the largest hospitals in the area," the UN statement said on Thursday. In air raids on Thursday, a civilian was killed in a Russian strike on the Idlib town of Latamneh, the Observatory said, while rebel shelling cost the life of a woman in regime-held territory outside the province. Elsewhere in Syria, eight civilians were among the 13 people killed in a car bomb near a checkpoint outside Afrin, the Observatory said. Turkish troops and Syrian proxies took control of Afrin from Kurdish forces they consider "terrorists" in March last year after a two-month air and ground offensive. "Among the victims, at least six are originally from Eastern Ghouta," a former rebel bastion near Damascus retaken by the regime last year, Mr Abdurrahman said. There was no immediate claim of responsibility for the blast, but a commander with a pro-Ankara faction accused Kurdish fighters. Since the Turkish-backed rebel takeover, the UN and human rights groups have documented widespread abuses in Afrin. The UN and Amnesty have also reported patterns of house appropriations by fighters and civilians bussed to Afrin during the surrender last year of Eastern Ghouta. Half of the Kurdish enclave's 320,000 residents have fled, according to a report by the UN Commission of Inquiry, and most are unable to return. Also on Thursday, several people were wounded in a car-bomb blast near a church in the Kurdish-majority city of Qamishli in north-east Syria. The attack was later claimed by ISIS. Endless rounds of UN-led peace talks have failed to stem the bloodshed in Syria. UN peace envoy Geir Pedersen, however, is pushing ahead with a 17-month-old effort to form a committee to write a post-war constitution. Both he and Damascus on Wednesday expressed "progress" towards forming the panel, whose composition has been the subject of dispute. Shored up by a series of Russian-backed victories since 2015, the regime wants to amend the current constitution, but the opposition wants an entirely new one. A September deal between Moscow and Ankara was supposed to avert a massive regime offensive on Idlib, but it was never fully implemented and Hayat Tahrir Al Sham took full administrative control in January. More than 570 civilians have been killed in regime and Russian air strikes on north-west Syria since late April, according to the Observatory. Rebel fire during the same period has killed more than 45 civilians in adjacent government-held areas.