Serbia's authorities are urging all migrants to move to the Balkan country's asylum centers during the cold spell that has gripped the country bringing heavy snow and extremely low temperatures. Greece's navy has sent a tank landing ship to the island of Lesbos to house refugees and migrants during a cold snap that has triggered public health warnings. A medical association on Lesbos said Tuesday that conditions at the main camp there were "inhuman" with migrants in tents exposed to freezing temperatures. Schools have been closed on Lesbos because of the bad weather, as a state of emergency was expanded to other areas in northern Greece, where snow has blocked roads and caused power and water outages.