The strikes, which the activists blamed on Russian and Syrian warplanes, came after an advance toward the city by government forces stalled, with the extremists taking back large areas in the surrounding province.
Syrian President Bashar Assad meanwhile designated a new prime minister to form a government following April’s parliamentary elections.
Activists from the group known as Raqqa Is Being Slaughtered Silently, which relies on residents to smuggle news out of Islamic State-held territory, said the air raids killed 18 people and wounded 28.
Both activist groups blamed the Russian and Syrian air forces for the raids, saying Damascus and its ally Moscow were pummeling Islamic State out of frustration at government losses earlier this week.
The Islamic State group retook large swaths of Raqqa province from government forces on Tuesday, just two days after Syrian troops managed briefly to seize Thawra, an Islamic State-held oil field, and threatened to retake the Tabqa air base from the militants.
