India, April 13 -- Hungary's longtime nationalist leader Viktor Orban conceded defeat on Sunday after his Fidesz party lost power in a landmark parliamentary election, ending 16 years of dominance as voters delivered a strong mandate for a pro-European course led by center-right challenger Peter Magyar.

With nearly half the votes counted, Magyar's Tisza party was projected to secure a decisive victory, winning approximately 135 seats, a two-thirds supermajority, in the 199-seat National Assembly.

"The election results are not final yet, but the situation is understandable and clear," Orban said at the Fidesz campaign offices. "The election result is painful for us, but clear."

The defeat represents a significant blow to Orban's interna...