The United States and its NATO allies denounced Russia on Monday for violating Turkish air space along the frontier with Syria, and Ankara threatened to respond if provoked again, raising the prospect of direct confrontation between the Cold War enemies.
NATO summoned the ambassadors of its 28 member states for an emergency meeting to respond to what Secretary-General Jens Stoltenberg called "unacceptable violations of Turkish air space".
Moscow's unexpected move last week to launch air strikes in Syria has brought the greatest threat of an accidental clash between Russian and Western forces since the Cold War.