Hungary's prime minister says the country will build a new, "massive" fence on its southern borders to defend against a possible surge in the number of migrants.

Prime Minister Viktor Orban, who earlier said migrants were "poison," said Friday on state radio that there may soon be a "greater need for security" and the fortified barrier would be able to stop "several hundreds of thousands of people," if needed. He did not say when construction could start.

Orban said the surge could take place if, for example, Turkey allows the millions of refugees living there to leave for Western Europe.

Hungary built fences protected with razor wire on its southern borders with Serbia and Croatia last year, when nearly 400,000 people passed through the country on their way west.