An Iraqi military statement says the Syrian air force has carried out a series of airstrikes against Islamic State group militants inside Syria, with one killing the group's leader in Raqqa, the IS de facto capital. Saturday's statement doesn't say when the airstrikes happened, but described the targets as ''the biggest positions for senior terrorists.'' The statement says the strikes targeted IS positions in Raqqa and the town of al-Bukamal and village of al-Dishaisha near the Iraqi border. Abu Bakir al-Habeeb al-Hakim used to work with al-Qaida and then the al-Nusra Front in Syria, the statement said. Another strike hit a gathering of suicide attackers who were planning to enter Iraq, according to the statement. Activists and residents say thousands of Syrians evacuated from their besieged towns have spent the night on buses at an exchange point as a much criticized population transfer deal stalls. You might also want to see this: Ahmed Afandar, a resident evacuated from his hometown near Madaya, says dozens of buses carrying children, women and men are not allowed to proceed toward rebel-held Idlib as planned. He said it is not clear what hinders the completion of the evacuation. Rami Abdurrahman, head of the Britain-based Syrian Observatory for Human Rights, says the Syrian government and rebels who negotiated the deal have differed over the evacuation of gunmen from the towns. A resident of Zabadani, another rebel-held town to be evacuated, Amer Burhan says no evacuation has taken place from there.