BAGHDAD— Under a blanket of tight security designed to thwart insurgent attacks, Iraqis went to the polls Sunday in an election testing the ability of the country's still-fragile democracy to move forward amid uncertainty over a looming U.S. troop drawdown and still jagged sectarian divisions.

Almost 20 million voters are eligible to turn out for the election, only the second vote for a full term of parliament since the 2003 U.S.-led invasion seven years ago this month. About 6,200 candidates are competing for 325 seats in the new parliament.

Insurgents have vowed to disrupt the elections with violence, but security was very tight across the capital where only select authorized vehicles were allowed on the streets and voters headed to the ballot box on foot. The borders have been sealed, the airport closed and hundreds of thousands of Iraqi military and police were on the streets.

Still, at least three explosions could be heard in the early morning hours although there was no information about whether anyone was hurt.

At one polling place in Baghdad's Karradah neighborhood, draconian security measures were in place with the school ringed by barbed wire, armed guards around the perimeter, and police using metal detectors to scan prospective voters.

The election has been viewed by many as a crossroads at which Iraq will decide whether to adhere to the sectarian politics — Shiites aligning with Shiites, Sunnis with Sunnis and Kurds with Kurds — that have defined its short democratic history. Or move away from the sectarian tensions that almost destroyed this Shiite majority country that was held down under Saddam Hussein's Sunni-minority rule.

Prime Minister Nouri al-Maliki is fighting for his political future against a coalition led by mainly Shiite religious groups — the Supreme Islamic Iraqi Council and a party headed by anti-American cleric Muqtada al-Sadr. He also faces a challenge from secular alliance led by former a secular Shiite, Prime Minister Ayad Allawi, who has teamed up with a number of Sunnis in a bid to claim the government.

President Jalal Talabani was among the first to vote Sunday morning in the Kurdish city of Sulamaniyah. Talabani's party, the Patriotic Union of Kurdistan, is enmeshed in a tight race with an upstart political party called Change which is challenging the two Kurdish parties who have dominated Iraqi politics for years. (AP)