"The 'empire' of US financier George Soros is working to make Europe a continent for migrants and will attack everyone hindering those efforts; not only Hungary, but the Czech Republic and Slovakia, too", Orban said.

"Some seek to flood Hungary with migrants, so that the country changes the same way as many western European cities have," he added.

Last week, Orban's chief of staff, Janos Lazar, sparked a row about how migrants changed Austria's capital, Vienna. Lazar said that the city "is dirtier, poorer and increasingly crime-ridden since migrants began living there".