"We can say with absolute certainty that we won," Orban told cheering supporters in Budapest. "These elections were free. Organised in a free country."
With 89 per cent of votes counted, Orban's Fidesz party was on 44.8 per cent of the vote, well ahead of the left-wing opposition alliance on 25.5 per cent.
The anti-Roma and anti-Semitic Jobbik party of the far-right looked to have increased its share to 21.0 per cent from 16.7 per cent at the last election in 2010.
"This is a great disappointment to those who wanted a change in government."
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Orban has made the most of the super-majority he won in 2010, with a legislative onslaught shaking up the media, the judiciary and the central bank.
Critics, including Brussels and Washington, have expressed concerns about vital checks and balances on key democratic institutions in the EU member state.
Many of these reforms have been written into a new constitution, meaning that even if the opposition were to win, it would need a two-thirds majority to change them.