CAIRO - Buses with loudspeakers blasting out songs about the importance of voting were touring central Cairo on the eve of the Egyptian presidential election, which analysts say lacks credible challengers to President Abdel Fattah al-Sisi.Bearing the seal of the Cairo municipality, the buses also displayed printed messages such as "be positive" and "participate in the 2018 presidential election."Polls open on Monday for three days in what is effectively a referendum on the performance of former military general Sisi, who is expected to coast to an easy victory against a little-known candidate who is considered a Sisi admirer.Sisi, who led the overthrow of Egypt's first freely elected president in 2013, wants a high turnout to affirm his legitimacy after all credible opponents dropped out in January, citing intimidation by the authorities after his main challenger was jailed.Opposition figures have called for a boycott of the election, while Sisi's campaign spokesman has said the government had not prevented any candidate from running.Sisi says his first four-year term has brought stability and security and he has urged Egyptians to vote in great numbers.The military said on Sunday that it had dispatched special vehicles around Egypt to assure Egyptians of a "secure climate" for voting, and policemen were seen on Friday handing out posters urging people to vote. Sisi promised to work for stability when he assumed power but has struggled to defeat an Islamic State insurgency in the Sinai Peninsula and contain other militant attacks across Egypt.His supporters argue that the security situation now is better than the unrest that rocked Egypt for years after the Arab Spring uprisings of 2011.MEDIA CENTRESisi won nearly 97 percent of the vote when he was first elected in 2014, but less than half of eligible Egyptians voted even though the election was extended to three days from two.The military on Sunday also said it would monitor local and foreign media coverage of the vote from a specially created media center that would operate 24 hours a day.Human rights groups say that a crackdown on press freedom has aimed to stifle dissent in the run-up to the vote, with Egyptian authorities calling for legal action against media outlets they deem to be publishing "fake news." Rights activists say that several local journalists have been arrested in recent months.Police and military personnel have taken over polling stations and set up nearby checkpoints to maintain security during the voting process, the military said.Two policemen were killed and five other people wounded in the coastal city of Alexandria in a bomb attack on Saturday that targeted the local security chief. There was no immediate claim of responsibility for the blast, though Islamic State released a video last month in which it warned Egyptians against voting and urged Islamists to attack security forces and leaders.