Originally posted by the Voice of America. Voice of America content is produced by the Voice of America, a United States federal government-sponsored entity, and is in the public domain. Car Bomb Targets Former IS Stronghold in Syria Sirwan Kajjo A powerful explosion on Wednesday rocked a town in northeast Syria, local sources told VOA. The car bomb attack, whichtook place on a main street near the center of Tabqa, wounded at least two security personnel and one civilian, the sources said. "There are definitely more casualties, but we don't have any details yet as local security forces have blocked the entire area," a Tabqa-based aid worker who requested anonymity for security reasons told VOA. No one immediately claimed responsibility for the attack, but the Islamic State terror group has carried out similar attacks in the past against U.S.-backed forces in the town and elsewhere in northeast Syria. Taken by SDF Tabqa, which is administratively part of Raqqa province, was under IS rule from 2014 until 2017, when U.S.-backed Syrian Democratic Forces took control of the town. "The city has been secured since we liberated it from [IS] terrorists," an SDF commander, who declined to be identified because he was not authorized to speak to reporters, told VOA."But these occasional incidents are expected as [IS] still has sleeper cells throughout the region." SDF officials said they had arrested members of IS-affiliated sleeper cells in two northern Syrian cities this week. "Counterterrorism units arrested five members of Daesh's sleeper cells in two separate successful raids in Raqqa and Manbij countryside," SDF spokesman Mustafa Bali said Wednesday in a tweet, using the Arabic acronym for IS. Earlier this week, IS took responsibility for a motorcycle explosion that wounded at least five civilians in the Kurdish-majority city of Qamishli in northeast Syria. .