Geneva, 15 March 2022 (dpa/MIA) - Some 3 million people have fled the war in Ukraine, a spokesperson for the United Nations' International Organization for Migration said on Tuesday. Among the refugees are over 150,000 third-country nationals, IOM spokesperson Safa Msehli wrote on Twitter. Millions more are said to be stuck within the country, either in their homes or as internally displaced people, with Russia's invasion now in its 20th day. According to government data collated by the UN Refugee Agency (UNHCR), the vast majority of Ukrainian refugees fleeing their country have arrived in Poland. Poland's border force reported on Tuesday that 1.83 million Ukrainian refugees had arrived since the war began. Some 453,432 have been counted in Romania, 337,215 in Moldova, 263,888 in Hungary and 213,000 in Slovakia, according to the UNHCR website. Some 142,994 refugees had fled eastwards to Russia, the agency said, citing the latest data from Moscow, while a relatively small number had fled to Belarus. Russia's long-feared invasion of neighbouring Ukraine began on February 24, triggering an exodus as people fled the violence. Russian forces have managed to encircle some cities, including the strategically important port of Mariupol on the southern coast, where several attempts to evacuate increasingly desperate residents have failed in recent days. A renewed attempt is planned for Tuesday, alongside eight other humanitarian corridors that Ukrainian authorities are seeking to establish, according to Deputy Prime Minister Iryna Vereshchuk. Elsewhere in Europe, governments were looking for ways to accommodate people seeking shelter. In Britain, the government announced a scheme on Monday for people to sign up to host refugees, with tens of thousands of households having registered by the following day. The Czech Interior Ministry announced on Tuesday that over 160,000 war refugees had been granted residence permits. The permits also allow the holder to work in the country. Almost half of those issued with permits are said to be women and children, with women making up 80% of the applications among adults. Ukrainian men were barred from leaving Ukraine shortly after the war erupted and urged to fight to defend the country. Based on mobile phone data, Czech authorities estimate the total number of Ukrainian refugees in the country to be between 200,000 and 270,000. Gym halls in Prague have been transformed into emergency shelters as the country struggles to house the arrivals.