In northwestern Syria, a Russian-backed offensive by Syria’s military on the last rebel-held province of Idlib has intensified in recent days, prompting hundreds of thousands of civilians to flee toward Turkey, where officials have sealed border crossings, leaving refugees to fend for themselves in squalid camps as fighting rages nearby. The U.N. said Thursday more than a quarter-million residents of Idlib and neighboring Hama province have been displaced by fighting in recent weeks, with reports of at least 160 civilian deaths. The Union of Medical Care and Relief Organizations says the toll is even higher, with at least 229 civilians killed and more than 700 wounded.