(ANSA-AFP) - SOFIA, 23 OTT - Bulgarians head to the polls Sunday in a presidential election overshadowed by security fears after a string of drone attacks on merchant ships in the Black Sea, seen as fallout from the war in Ukraine. Four vessels were struck off Bulgaria's coast this month in the latest suspected spillover from Russia's 2022 invasion of Ukraine, bringing the conflict closer to the EU and NATO member state. While Prime Minister Rumen Radev says the attacks appear to serve Russian interests, his government insists there is so far no evidence directly linking Moscow to them. Incumbent President Iliana Iotova, a Radev ally who favours dialogue with Moscow, is the frontrunner for the largely ceremonial post, polls show. Her main challenger is expected to be Andrey Gyurov, a banker and former caretaker prime minister backed by the pro-Western opposition. Iotova, 61, took over as president earlier this year when Radev stepped down to run in parliamentary elections. Radev's landslide victory ended years of political instability that saw a succession of pro-EU governments lead the Balkan country of 6.4 million people. While largely ceremonial, the presidency carries veto powers, a role in appointing senior officials and command of the armed forces. According to a Market Links poll published Wednesday, Iotova is expected to win 47.3 percent of the vote, against 30.6 percent for Gyurov. If successful in a runoff set for November 1, she would become the first woman ever elected president of Bulgaria. (ANSA-AFP).