Ukraine says Donetsk 'anti-terror operation' under way
15 April 2014 Last updated at 19:12 BST
Ukraine's acting President Olexander Turchynov has announced the start of an "anti-terrorist operation" against pro-Russian separatists.
He told parliament it was being conducted "stage by stage, in a responsible... manner".
Hours later, gunfire was heard at an airbase which officials said had been in the hands of militants.
Daniel Sandford reports.