Bulgarians went to polls on Sunday to elect their next president among seven candidates including the incumbent Socialist President Georgi Parvanov.
Polling stations in the Balkan country opened at 6 a.m. (0300 GMT) and will close at 7 p.m. (1600 GMT).
Parvanov, 49, who is running as an independent, is widely expected to win the election, as earlier opinion polls indicated that he could garner between 50 and 58 percent of the votes.
However, under the Bulgarian law, voter turnout must be above 50 percent and a candidate must get over 50 percent of the total valid votes for him or her to win an outright victory.
As polls indicated that less than 40 percent of Bulgaria's 6.4 million eligible voters will turn out, Parvanov could end up in a run-off against ultra-nationalist Volen Siderov a week later on Oct. 29.
Siderov, 50, has been tipped to win between 20 and 25 percent of the votes.
Preliminary results will be available 90 minutes after the end of the voting process. The final results will be announced in the early afternoon on Tuesday.
The Bulgarian presidency is largely ceremonial, but is entitled to legislative veto power.
Source: Xinhua