U.N. Secretary-General Ban Ki-moon voiced concern on Friday about increasing border restrictions in the Balkans and Austria for migrants and refugees streaming toward Europe and urged all countries to keep their frontiers open. Ban's spokesman Stephane Dujarric said Turkey is hosting more than 2.6 million refugees and asylum seekers, and the influx to Greece from Turkey continues unabated. Seven European states have restored border controls within the Schengen passport-free zone, and others have said they would unilaterally tighten border controls unless a deal with Turkey to curb the flow of migrants from conflicts in Syria, Iraq, Afghanistan and other countries shows results soon.