BEIRUT - At least 63 people, half of them civilians, were killed when Syrian war planes struck the northeastern city of Raqqa on Tuesday, according to the Syrian Observatory for Human Rights, which monitors the war in Syria.Syrian government officials were not immediately available for comment.Rami Abdulrahman, who runs the Britain-based Observatory, said 10 war planes struck at least 10 times in Raqqa, a stronghold of the ultra-hardline group Islamic State."The majority of the strikes were in the eastern part of the city," Abdulrahman said. "At least 36 of those killed are civilians. As for the rest, we are not sure yet if they were fighters."Islamic State, which has seized wide expanses of territory in Iraq and Syria, drove the last Syrian government forces out of Raqqa province in late August. Its fighters seized an air base then, capturing and later executing scores of Syrian soldiers.