BUDAPEST (Reuters) - Hungarian Prime Minister Viktor Orban's ruling Fidesz party extended its lead ahead of a six-party opposition alliance in a late-February survey by the pollster Median coinciding with the start of the Russian invasion of neighbouring Ukraine.

       The poll, conducted between Feb. 22 and 26, put support for nationalist Orban's Fidesz at 39% of the electorate, unchanged from December levels, while the opposition shed 2 points to 32%.

       Orban, who has showered the electorate with tax cuts and other benefits worth 1.8 trillion forints ($5.23 billion), will on April 3 face a united opposition front for the first time since taking office in a 2010 election landslide.

       The opposition alliance includes the Democratic Coalition, the Socialists, liberals and the formerly far-right, now centre-right, Jobbik. Its candidate for prime minister is Peter Marki-Zay, an independent who is currently mayor of Hodmezovasarhely, a town in southern Hungary.

       The ranks of the undecided increased to 20% from 13% in December, which the survey said reflected uncertainty within the opposition camp and falling support for fringe parties, such as the far-right Our Homeland, or the Two-tailed Dog Party.

       The survey said Orban's Fidesz had the strongest backing among older people, rural voters and the poor, while the opposition had larger reserves among young voters, urban populations and wealthier people.

       With a little more than four weeks left until the ballot, another challenge for the opposition is a growing sense among the electorate that Orban is likely to get re-elected, with 67% expecting a Fidesz victory, up 4 points from December.

       Only 45% of its own supporters see an opposition victory, the survey said, adding however that it could not yet gauge the impact of renewed falls in the forint to record lows and the escalating military conflict over the borders.

       DATE AGENCY FIDESZ OPPOSITION UNDECIDED

       Feb 22-26 Median 32 20

       39

       Jan 31-Feb 9 IDEA 38 34 13

       Feb 2-10 Zavecz 38 36 20

       Jan 20-25 Republikon 36 34 22

       Jan 4-14 IDEA 39 37 10

       Dec 4-7 Median 34 13

       39

       Dec 9-14 Republikon 33 36 24

       Nov 2-12 Zavecz 37 41 14

       Nov 2-3 Nezopont 56 42 2

       Oct 25-29 Republikon 32 38 30

       Oct 11-19 Zavecz 35 39 23

       Sept 29-Oct 4 Median 37 37 17

       Oct Szazadveg 50 44 6

       Sept Zavecz 37 38 23

       Sept 20-21 Nezopont 53 45 N/A

       Aug 23-25 Nezopont 52 46 N/A

       ($1 = 344.2800 forints)

       (Reporting by Gergely Szakacs; Editing by Alison Williams)