The International Organisation for Migration estimated that 309,356 people had arrived by sea in Greece as of September 10, with another 121,139 arriving in Italy, 2,166 in Spain and 100 Malta. It comes as Hungary's prime minister has warned migrants that if they cross the border illegally they will be arrested from next week. Viktor Orban said migrants had rebelled against the country's laws and had failed to co-operate with authorities in recent days.