Clashes between anti-government fighters and regime forces killed more than 50 combattants on both sides in northwestern Syria on Tuesday, a war monitor said. At a meeting in Moscow, the presidents of Turkey and Russia expressed “serious concern” over the violence in Idlib province. “Violent clashes east of the town of Khan Sheikhun broke out at dawn after jihadist and opposition groups attacked regime positions,” Observatory chief Rami Abdel Rahman said.