those are air raid sirens and they're near constant in kyiv. overnight explosions in that capital city. missiles, mortars, tanks and russian troops shattering the uneasy relative calm of the past few months. the initial wave of attacks appear to be coming from all different directions. and so far, it remains unclear if ukrainian forces have actually been able to mount any sort of effective resistance. in ukraine's second largest city, the subway terminal is now serving as a bomb shelter. cnn's clarissa ward was there earlier today. >> we're talking hundreds of people spread out throughout this entire subway station.