The ruling right-wing GERB party candidate, Rosen Plevneliev, emerged as the front-runner in Bulgaria's presidential race ahead of a second-round run-off, after the release of partial results Monday.

Plevneliev, who shot to popularity as former construction minister only two years after entering politics in 2009, had 39.6-percent support, with 40 percent of the ballots counted, the central electoral commission said.

The Socialist Ivaylo Kalvin was second with 29.7 percent and independent candidate and ex-European commissioner Meglena Kuneva trailed third with 14 percent, commission spokesman Biser Troyanov said.

Failure by any of the runners to win outright majority of over 50 percent of the ballots cast authomatically sends the two top contenders to a run-off on October 30.

Plevneliev hailed his commanding lead for presidency as historic on Sunday night but analysts predicted a tough battle in the run-off.

In simultaneous municipal elections, GERB won the mayoral seats in Sofia, the Black Sea city of Burgas and two smaller towns in the first round and faces October 30 run-offs in another 20 towns.

The Socialists meanwhile won in the northeastern town of Shumen, while the Turkish minority MRF party secured its all-time bastion of Kardzhali.

MRF's powreful leader Ahmed Dogan meanwhile urged the Turkish minority "to do the necessary so that Kalfin receives the support he needs" to beat Plevneliev in the run-off.

Vote-buying and voters' pressure concerns had marred the run-up to the vote, prompting missions by international obresrvers from the Organization for Security and Cooperation in Europe (OSCE) and the Council of Europe Parliamentary Asembly (PACE).

Full offical results are expected later Monday.