The ongoing leadership election of the Unified Progressive Party (UPP) has been suspended due to errors in its server for online voting, party officials said Wednesday, amplifying uncertainties for the left-wing party beleaguered by an escalating factional conflict over alleged primary rigging earlier this year.

The minor party with 13 seats in the 300-member National Assembly is set to elect its new leadership this week after a faction of alleged pro-North Korean forces lost power after it was found to be involved in the rigging of the party's proportional representative primary for the April general election.

A rival faction consisting of reformists is seeking to seize control of the crisis-stricken party through the election.

The UPP's five-day leadership election has been underway since Monday to elect its new chairperson, with the outcome expected to be announced on Saturday by adding up online, mobile and on-site voting results.

According to party officials, the server for online voting stopped at around midnight due to unidentified causes, resulting in a loss of the data collected since Monday.

"Due to server problems, part of the voting results are missing and it is hard to restore them," said an official of the party's reformist emergency committee.

The UPP used a server provided by a local company, which had its computers confiscated last month during the prosecution's investigation into the alleged primary vote irregularities, the official said.

The party plans to hold an emergency meeting later in the day to discuss whether to cancel the ongoing vote and conduct another one.

The online voting was suspended just hours after the party's fact-finding team announced a second round of investigation results late Tuesday regarding the primary held to pick the party's proportional representative candidates for the April 11 elections, admitting that several votes were cast under the same Internet Protocol addresses.

The announcement of the investigation results sparked strong backlash from the anti-reform party members who argue that the fact-finding team had disregarded a report that pointed to similar illegal voting committed by its rival reformist group.

The race for the chairmanship is a two-way competition between interim chief Kang Ki-kab and Kang Byung-gee, who represents mainstreamers allegedly taking a pro-North Korea stance.

Kang Ki-kab represents the reformers and has pledged to expel Reps. Lee Seok-ki and Kim Jae-yeon ― the two key figures in the party's vote-rigging scandal in the April vote. (Yonhap News)