At least 32 Islamic State fighters were killed and 40 more wounded in the Raqqa, Syria on Sunday after a series of air strikes carried out by a U.S. air force.

US pilots reported that they hit more than 15 ISIS targets in and near Raqqa city, which was confirmed by Britain Observatory for Human Rights in Syria.

In the meantime, Syria’s president, Bashar al-Assad, told The Sunday Times that bombing will increase the risk of terrorist attacks by sleeper cells in Europe unless there is a concerted effort to destroy Isis on the ground.