Rumen Radev, the socialist-backed candidate, is on the lead in the first round of Bulgaria's presidential elections, exit poll data shows.

Gallup Internatioinal has projected 24.9% support for Radev, while the candidate of the main ruling GERB party, Tsetska Tsacheva, has ranked second, having mustered 22%.

Alpha Research, another pollster offering exit poll results, suggests Radev has garnered 25%, with Tsacheva's support at 22.1%.

According to Alpha Research, third, lagging far behind, is nationalist candidate Krasimir Karakachanov, at 14.9%.

Fourth, surprisingly, comes businessman Veselin Mareshki (10.9%) who runs as an independent candidate, followed by Plamen Oresharksi, the controversial ex-PM who has got with 7.1%

Reformist Bloc's Traycho Traykov, at 7.1%, is expected to come sixth with 6%, while Ivaylo Kalfin of ABV garners 3.8%, according to the exit poll.

The newly introduced option, "Not Voting Anyone", gets 6.2%.

Gallup data suggest Karakachanov got 15.4% of the vote, followed by Mareshki at 11.7%, Traycho Traykov with 6.1%, and Plamen Oresharski who mustered 6.0%. Ivaylo Kalfin earned 3.2%. The "protest vote" is measured at 5.8%.

GERB party of Prime Minister Boyko Borisov is yet to comment officially, with Regional Development Minister Lilyana Pavlova warning there is one more our before polls close. 

But Borisov earlier said he would step down if Tsacheva doesn't win the first round.

Voter turnout was more than 52.4% as of 19:00 local time, Alpha Research pollster says. Gallup's projection is for 53%.

As for the referendum, the activity is 45.3% and 47% citing data of the two agencies, respectively.

Voter activity data does not include estimates for expat voters. 

More to follow.