in the southern city of mariupol, where some 2,000 ukrainians troops have been making a desperate last stand. ukraine says russian forces have launched an all out assault on the steelworks, where about 200 civilians are still believed to be trapped, sheltering inside bunkers, including 30 children. moscow says humanitarian corridors will open for three days to allow people to leave. the hope is that civilians can escape the area to safety but ukraine has previously accused russian forces of continuing attacks after announcing ceasefires. this is unverified footage released by russian backed separatists. experts say it appears to show thermobaric or vaccum bombs being dropped on the industrialfacility. it is unclear when the footage was filmed. denys propokenko, commander of ukraine s azov brigade which is defending the steelworks,