Ballot boxes from across Ireland's 39 constituencies were opened at 9 a.m., the BBC reported.
The exit poll, commissioned jointly by Irish national broadcasters RTÉ and TG4, as well as The Irish Times and University College Dublin, indicated that the ruling Fine Gael led by Prime Minister Leo Varadkar secured 22.4 per cent of first preference votes, closely followed by Sinn Fein (22.3 per cent) and Fianna Fail (22.2 per cent).
This is the first time in Ireland's history when there are three major parties competing with each other on almost equal footing instead of the two in the past elections, said RTE.
The results of the exit poll indicate that it will be difficult to form a new government as both leaders of Fine Gael and Fianna Fail had said that they would not form coalition with Sinn Fein in the future government, Xinhua news agency reported.
According to Irish laws, whoever wins the most number of the 160 seats in the Dail, the lower house of the Parliament, will be empowered to form the new government so long it can win the support from half of the members of the Dail either through coalition with or seeking support from other parties or independents.
In the last Dail, which was dissolved on January 14, Fine Gael had the largest number of seats which stood at 47, followed by Fianna Fail (45) and Sinn Fein (22).
There were a total of 515 candidates, either fielded by different political parties or running on their own, competing in the general election on Saturday.
The exit poll was issued after the voting ended at 10 p.m.
A total of 3.4 million people were eligible to vote.
Preliminary counting showed that the national turnout in the 2020 general election could be higher than that of the 2016 election, which stood at 65.1 percent, according to local media reports.
Results were expected later in the day.