Ten people were killed and 20 wounded on Saturday in a suicide car-bomb attack in Raqqa, a former stronghold of the Islamic State (IS) group in north Syria, a rights watchdog said. The explosion claimed the lives of five civilians and five soldiers of the Syrian Democratic Forces (SDF), a Kurdish-Arab alliance backed by Washington that wrested the city from IS in October 2017, according to the Syrian Observatory for Human Rights. The incident underlines the continued threat of IS sleeper cells in northeastern Syria, according to Kurdistan24’s website. The attack, for which no one has claimed responsibility, was preceded by a bomb explosion that left several people wounded in another part of the city frequently targeted by IS, the Observatory said. The explosion took place at the al-Naim square, where IS had carried out beheadings when it was in control of the city. Observatory director Rami Abdel Rahmane told AFP: "The car bomb attack was targeting an SDF position." “The SDF is in a difficult phase of stabilization because it has multiple enemies - be they IS, the Assad regime and its allies, especially Iran and Turkey,” Nicholas A Heras, a Middle East security analyst at the Washington-based Center for a New American Security, told Kurdistan24. “Raqqa is a vulnerable location because it is a large area where there are a lot of people moving into and out of the city.” According to Heras, this means the SDF’s enemies have more opportunities to place their operatives in Raqqa and carry out attacks. Moreover, Heras said that Raqqa is a high-value target because the US-led coalition has made it a model of how to rebuild in the aftermath of IS. On 9 April, a double bombing claimed by IS killed 13 people, mostly civilians, in the group's former bastion. Ambushes and hit-and-run attacks have continued in both countries, with IS militants still scattered across the Syrian desert. AFP.