About 9.8 million Greek voters are expected to cast their ballots on Sunday, with polling stations opening at 7:00 a.m. (0400 GMT) nationwide for the first round of the municipal and regional polls.

The elections are seen as the first test for the government and opposition parties ahead of next Sunday's elections for the European parliament.

Approximately 10,000 seats in 13 prefectures and 326 municipalities are being contested, most of which, the pre-election surveys showed, will be decided in the second round on May 25.

For the first time local administrators who are elected in this year's polls are to serve for five years instead of four as in the past, after a recent local administration reform.

Under the Greek Constitution, candidates at local elections do not run under the names of parties rather than independent electoral lists.

However, most candidates are clearly supported by parties and their victory or defeat is estimated as a gain or loss for parties.

The handling of the four-year debt crisis and prevailed in the pre-election campaign, as it happened in the previous local elections in October 2010.

The spotlight traditionally is on the races for the post of Mayor of the Municipality of Athens and Regional Governor of Attica.

Latest surveys showed that incumbent Mayor Yorgos Kaminis with the support of centre- Left and liberals holds a five percent lead over the second candidate former Tourism and Education Minister Aris Spiliotopoulos of the conservative ruling New Democracy party.

In the race for Regional Governor the incumbent Yannis Sgouros who is supported by the co-ruling socialists is running neck and neck with main opposition Radical Left SYRIZA party candidate Rena Dourou, according to pollsters.

Polls close at 19:00 p.m. (1600 GMT). Exit polls will be released shortly afterwards, with the first official estimates expected shortly before midnight and the final results on Monday morning.