Bulgarian voters have backed the introduction of a first-past-the-post system, compulsory voting, and a drastic slash in state subsidies handed to political parties, exit poll data shows.

A referendum on three issues is being held on Sunday alongside the presidential election.

Some 74.2 percent have backed the introduction of a majority system, while 19.1% were against, according to Alpha Research pollster. Gallup data puts the numbers at 79% and 16.4% respectively.

With regard to compulsory voting, 65.6% have backed mandatory elections, while 28.2% have opposed, according to Alpha Research. Gallup's figures are 70.6% and 26.5%, respectively.

The cut in state subsidies from BGN 11 to BGN 1 per vote has been backed by 78.1% of those who took part in the referendum, with 15.9% having ticked "no". Gallup's numbers are 80% and 16.3%

Figures do not make up 100% as there is a share of between 4 and 6% of voters who did not respond to some of the questions, according to the polling agencies.

The referendum's validity now hinges on the turnout, which is reported as nearing 50%.

However, results are yet to be announced for each separate question as turnout will be calculated for each of the three issues.