The heaviest security was around Pearl Square in the Bahraini capital Manama, which was once the hub for Shiite protesters demanding greater rights from the ruling Sunny monarchy. The area was ringed by barb wire and lines of armored police vehicles amid calls by anti-government factions to try to reclaim control of the site.
The special elections were called to fill 18 parliament seats abandoned by Shiite lawmakers to protest the harsh crackdowns since February in the strategic nation, which is home to the U.S. Navy's 5th Fleet.
More than 30 people have died in the unrest and hundreds have been arrested, including activists sentenced to life in prison after being charged with plotting to overthrow the ruling system.
Main Shiite factions have vowed to snub the voting in a message of defiance. On Friday, scattered clashes broke out in mainly Shiite areas and Bahrain's most senior Shiite cleric, Sheik Isa Qassim, denounced the government as leading a "fake democracy."
Shiites are the majority in Bahrain, but claim they face widespread discrimination and are blocked from high-level military or political posts. Among the demands is a European-style system for an elected government, including the prime minister.
Bahrain's parliament has little direct powers, but it carries important symbolism as part of limited political reforms started about a decade ago. The expected boycott is almost certain to leave the parliament totally in pro-government hands and deepen the country's rifts. Four of the candidates have already been declared winners by running unopposed or after rivals dropped out.
Bahrain's leaders, meanwhile, have backing from powerful Gulf neighbors that fear any cracks among the region's ruling kings and sheiks. A Gulf force, led by Saudi Arabia, was dispatched to Bahrain in March to help prop up the 200-year-old Sunni dynasty.
But the protests across the region have stirred some small steps toward more political openness.
The United Arab Emirates also holds elections Saturday for seats on a national advisory council, which has no legislative powers but is promoted by Emirati officials as part of a widening "experiment" in allowing a greater public voice in affairs. The UAE's elections will be decided by about 129,000 hand-picked voters.
Later this month, Saudi Arabia plans to hold municipal elections after a nearly two-year delay. Woman, however, will be still barred from participating or voting.