Slavyansk, Ukraine (CNN) -- Deadly street fighting, helicopters shot down and civilians being used as human shields. That was the picture that emerged Friday in southern Ukraine as violence escalated amid reports that dozens of people were killed in a fire and still more were shot dead or wounded in street fighting, raising the question of whether the country can stave off a possible civil war. The violence -- pitting pro-Russian separatists against Ukrainian forces and those who support the government in Kiev -- prompted an emergency meeting of the U.N. Security Council, with Russia demanding an end to what...