BBC News reports at least 36 civilians have been killed in air strikes by Syrian government warplanes on the Islamic State-held northern city of Raqqa, activists say. Most of the casualties were caused by two strikes in quick succession on an industrial area, the UK-based Syrian Observatory for Human Rights reported. One opposition activist network said more than 80 people had died. Syrian government and US-led coalition aircraft frequently bomb Raqqa, which IS has made into a stronghold. Activists say most of the casualties from the raids have been civilians. The Syrian Observatory said Tuesday's air raids had targeted a popular market near Raqqa's museum as well as the industrial area where two explosions caused most of the casualties.