Early voting for the presidential election began on Thursday at 3,568 polling stations nationwide as voters prepare to elect a successor to former President Yoon Suk Yeol, who was ousted over his failed martial law bid.

The two-day voting period began at 6 a.m. and will close at 6 p.m. Friday, according to the National Election Commission (NEC).

As of 8 a.m., the voter turnout stood at 2.24 per cent.

Currently, six hopefuls are vying for the presidential office, reports Yonhap news agency.

The latest poll on the presidential election, published Wednesday, showed Democratic Party (DP) candidate Lee Jae-myung in the lead at 49.2 per cent, followed by Kim Moon-soo of the People Power Party with 36.8 per cent. Lee Jun-seok of the minor New Reform Party came in third with 10.3 per cent support.

The single five-year term of the next president will begin immediately following the election.

The DP's Lee will cast his ballot Thursday at 10 a.m. in Sinchon, western Seoul, while Kim is scheduled to vote in Incheon's Gyeyang district during his campaign stop there.

Meanwhile, the Seoul Metropolitan Police Agency said on Wednesday it will mobilise about 6,400 armed police officers to support the transport of ballot boxes for the June 3 presidential election, signalling an intent to quell the controversy over vote rigging.

The agency also said it will deploy about 6,200 police officers to guard or patrol 426 early voting stations and 2,260 main voting stations throughout the capital. In addition, 1,250 officers will be sent to 25 ballot-counting stations to maintain order, it noted.

Police plan to strengthen their security posture during the early voting on Thursday and Friday and enforce the highest-level security alert on June 3, the agency said.