By Aditi Sangal, Maureen Chowdhury, Adrienne Vogt, Meg Wagner, Helen Regan, Travis Caldwell and Melissa Macaya, CNN The Russian warship Moskva has sunk, according to Russian state news citing the Russian defense ministry. Conflicting claims have emerged: Ukraine says it hit the vessel with missiles, but Russia says a fire broke out on board. Russian preparations continue in the east for an offensi