The Hungarian opposition party Tisza leads ahead of Prime Minister Viktor Orban's ruling Fidesz two days before the parliamentary elections scheduled for Sunday, according to the latest polls published in the newspaper Nepszava.

Orban faces the biggest challenge in his 16-year rule, but the large number of undecided voters means the election outcome remains uncertain.

Tisza, led by former government insider Peter Magyar, enjoys the support of 52 percent among decided voters, while Fidesz is supported by 39 percent, according to the results of a poll by the Publicus institute in which 1,000 respondents participated.

When all voters are taken into account, 38 percent support Tisza and 29 percent support Fidesz. Around 25 percent of respondents said they have not yet decided who they will support.

The elections in Hungary are being followed with particular attention by the European Union and neighboring countries, given Orban's controversial foreign policy and his close relations with Moscow and Beijing.