Fidesz won 48 per cent of the vote, well ahead of the left-wing opposition alliance on 27 per cent, with the far-right Jobbik winning 18 per cent, the exit polls showed.
It was unclear, however, whether this would be enough for the right-wing Orban, 50, to retain his two-thirds majority in parliament.
Official results were due later today.
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.
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"The Internet is where you go to find out what is really happening in Hungary," Aranka Szavuly, a freelance journalist fired from state media in 2011, told AFP.
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.
Since then he has turned the Fidesz movement that he formed with like-minded young liberals into a potent political force.
He was first elected prime minister aged just 35 in 1998, but lost to the Socialists four years later before returning to power in 2010.
Orban says his changes are aimed at turning Hungary into a "race car" after eight years of economic and political Socialist mismanagement before 2010 had reduced it to an "old banger".