BEIRUT — An explosion in a village in northwestern Syria near the border with Turkey killed at least 29 people on Thursday, including several Turkey-backed opposition fighters, Syrian activists said. The attack was quickly claimed by the Islamic State group.

The deadly bombing underscored the complex layers of the Syrian conflict, where a civil war between Syrian President Bashar Assad’s forces and the rebels trying to oust him is taking place alongside a militant insurgency and an international war against the Islamic State group.

Meanwhile, activists in the northern city of Aleppo said it was calmer on Thursday after Syria’s military command announced the night before it would scale back bombardment of the contested city to allow civilians to leave besieged rebel-held neighborhoods.

“There were shellings and air raids, but it was less than in previous days,” said activist Bahaa al-Halaby, speaking from Aleppo province near the city.

The Britain-based Syrian Observatory for Human Rights said that although airstrikes have almost stopped on the besieged eastern rebel-held neighbohroods of the city, government forces were pushing ahead in their ground offensive. The Observatory and state media said government forces advanced in Aleppo’s northern neighborhood of Bustan al-Basha where troops captured a sports complex and a nearby housing compound.

Meanwhile, Assad denied reports that his government is targeting hospitals and civilian infrastructure. Syrian opposition activists and international relief agencies have said Syrian and Russian warplanes have been hitting hospitals and infrastructure in Aleppo, which has been the epicenter of the Syrian civil war in recent months.

Assad told Denmark’s TV2 station that “to say that this is our aim as a government, (that) we give the orders to destroy hospitals or schools or to kill civilians, this is against our interest.”