Malta is voting in snap general elections called against a backdrop of corruption allegations that have tarnished Prime Minister Joseph Muscat's government.
Malta, which currently holds the rotating EU presidency, has also warned that it has become the target of cyberattacks that experts say come from Russia.
Opinion polls indicate that 43-year-old Muscat's Labor Party (PL) will retain power with a reduced majority.
Up to 30 percent of the roughly 340,000 registered voters remain undecided, giving hope to Simon Busuttil's opposition Nationalist Party (PN) of a last-minute swing in voters' opinion in his direction.
Muscat called the election a year early after his wife, Michelle, was accused of being the beneficial owner of a secret Panamanian shell company used to bank unexplained payments from Azerbaijan's ruling family.
The prime minister's chief of staff, Keith Schembri, has admitted having his own, previously undeclared Panama-registered company.
Media reports also alleged that Schembri accepted bribes from the sale of Maltese passports to wealthy Russians.
Last month, Muscat said that Malta's security services had been alerted to possible Russian interference in local affairs.
Relations between Russia and Malta have soured recently, mainly after Valleta's refusal to allow Russian warships heading to Syria to refuel in Malta.
Sources in the Maltese government said the country had become a target of increasing cyberattacks.
Security experts say the Fancy Bear -- a hacking collective that is often associated with the Kremlin -- is a prime suspect.
The election is taking place weeks after the country's tax policies also came under scrutiny in a journalistic probe depicting the small Mediterranean island state as a tax haven.
Polls close at 10 p.m. local time (2000 GMT/UTC). First results are expected on June 4.