(CNN) -- A gunman killed three people and wounded at least five at the house of a mayoral candidate in the Philippines before polls opened on Monday, a military spokeswoman said.
The attack happened around 2:30 a.m. (2:30 p.m. Sunday ET) when an unidentified gunman raided the house of a mayoral candidate in Zamboanga del Sur province, said spokeswoman Steffani Cacho. The incident is under investigation, she added.
More than 50 million ballots have been printed with a dizzying number of candidates to choose from -- nine for president alone, among them front-runner Sen. Benigno Aquino III, son of a former president; and Joseph Estrada, a former president himself.
Family dynasties also play a role: Former first lady Imelda Marcos is running to fill the Congressional seat of her son, Ferdinand "Bongbong," who is running for Senate, while her Congresswoman daughter Imee is running for governor.
Boxing champion Manny Pacquiao also threw his hat in the ring: He's running for Congress too.
In all. voters must fill some 17,000 other positions at the executive, legislative and local levels.
A faulty test run of automated machines raised questions as late as Wednesday of whether the elections would even happen. A postponement would have stirred fears of a power vacuum on June 30 when President Gloria Macapagal-Arroyo is scheduled to end her nine years in office.
Polls opened to crowds of waiting voters, CNN's Arwa Damon reported from Manila.
"People are very excited," Damon said, adding that the election-day mood was "tinged with anxiety."
Polls were scheduled to remain open until 6 p.m. local time (10 a.m. GMT).
"It's a very crucial litmus test to our democracy, our fragile democracy," said Leila De Lima, chairwoman of the Commission on Human Rights of the Philippines, which will be serving as an independent election monitor. "The administration has been hounded by issues of corruption, human rights violations. People are looking forward to a new administration that will hopefully usher in meaningful changes. So, it's very, very important."
"The right of suffrage is a fundamental human right," she added.
The Philippine National Police (PNP) has been placed on nationwide full alert since last week, with all leaves canceled, and all 130,000 officers required to report for duty.
An election ban on liquor sales and public consumption went into effect Sunday, with violators subject to one to six years in prison. Exemptions are made for hotels and tourist-oriented establishments with prior approval. A nationwide gun ban has already been in force since January 10 at the start of the election period.
Vote buying is "currently the most common form of cheating," the PNP quoted its chief and director-general Jesus Verzosa as saying.
Whereas in the past, people were paid to vote, this time they are paid to waive their right to vote and have their index fingers marked with ink, making them ineligible, according to PNP. Reports indicated some candidates were willing to pay identified supporters of their opponents not to vote, the PNP said on its Web site.
The proliferation of guns and private armies, particularly those attached to political families, has contributed to a violent atmosphere, particularly in the country's southern province of Maguindanao, where 57 people were massacred in November.
The transparency of the election process also has also been called into question. Election watchdog group Kontra Daya on Saturday condemned the Commission on Elections' approval of presidential son Juan Miguel Arroyo as first nominee of a political party made up entirely of security guards. The party is running as one of 187 "party-list groups" that are designated as marginalized and underrepresented and would together comprise one-fifth of the House of Representatives.
Last month Kontra Daya identified 40 questionable party-list groups, showing their links to various people in the Arroyo administration or the president's family, including her sister-in-law, who represents a party of small entrepreneurs.
Not to be outdone is the inclusion on millions of ballots of a person whose name may appear at the top of the list of presidential candidates -- and above Aquino's -- despite being disqualified in March: Vetellano Acosta.
The Commission on Elections said Acosta, who is listed under the "KBL" party founded by Ferdinand Marcos, would remain on the ballot because so many ballots had already been printed.
CNN's Elizabeth Yuan contributed to this report.