BEIRUT — A Syrian military aircraft crashed into the de facto capital of the self-proclaimed Islamic State group on Tuesday, killing at least eight people, as thousands of residents fled to nearby villages in anticipation of expected US airstrikes against the militants, activists said. It was not immediately clear whether the plane that slammed into the northeastern city of Raqqa was hit by anti-aircraft fire or experienced a technical failure, according to an activist based in the city and the Britain-based Syrian Observatory for Human Rights. The Raqqa-based activist, who goes by the name Fourat Alwfaa, said eight people were killed in the crash, including members of two families after the aircraft plowed into their home. The Observatory said there were casualties, but did not have a concrete figure. The so-called Islamic State group controls a proto-state that stretches from northern Syria across much of northern and western Iraq. Raqqa, an ancient city on the Euphrates River with a prewar population of 500,000, serves as the extremists' stronghold in Syria. — AP