Iraq's Independent High Electoral Commission (IHEC) said in a statement that "the voting process was successful and went smoothly throughout the country without major violations."
Riyadh al-Badran, an IHEC senior official, told the official Iraqiya TV channel that "he would not announce the results of the early ballot by the security forces, prisoners and the voting abroad. The final results of the election will be announced in 24 hours after the end of the general vote."
Dozens of thousands of security forces lined up at polling centers across Iraq, as they began casting ballots at 7:00 a.m. (0400 GMT) until 6:00 p.m. (1500 GMT).
More than 943,000 voters were scheduled to cast their ballots at 494 polling centers across the country during the day, two days ahead of the scheduled election date.
Also on Thursday, thousands of Iraqi expatriates continued casting their ballots in some 130 polling centers in 21 countries across the world.
The 2018 parliamentary election is the first since Iraq's historical victory over the militant Islamic State group in December last year, as over 24 million Iraqis are eligible to vote in 4,148 polling center across Iraq for a new parliament, which they hope will bring change to the economic and security situations in the country.
Around 7,000 candidates, representing 205 political entities are vying for the 329 seats.
Iraq's previous general election was held on April 30, 2014, when the Iraqis elected 328 lawmakers for the parliament.