Egypt's Constitution Party, which backs leftist candidate Hamdeen Sabahi in Egypt's ongoing presidential elections, has expressed unease over the electoral process after authorities unexpectedly extended the voting period, condemning alleged harassment of its monitoring team by polling staff.

In a statement emailed to Ahram Online, the party said the decision taken by the Presidential Elections Commission (PEC) to add an unscheduled third day to the vote "raises much suspicion and poses questions pertaining to its motives and [the surprise move's] possible implications," given the "nearly empty" polling stations reported by its monitoring team over the "sufficient" two-day period.

According to state news agency MENA, the party stated that it would withdraw its representatives from a number of polling stations and refrain from monitoring the Wednesday vote, in protest to the "lack of transparency", especially after the PEC's surprise decision to extend the vote. The party's statement to Ahram Online, however, made no mention of such measures.

The PEC extended the originally planned voting period by a third day on Tuesday evening, in a bid to improve the lower than expected turnout.

The liberal Constitution Party, founded after the January 2011 uprising by Nobel laureate Mohamed ElBaradei, said it was seriously troubled by the harassment inflicted on its representatives by administrators and supervising judges at polling stations, as well as by assaults on its members by supporters of presidential frontrunner former army chief Abdel-Fattah El-Sisi, the latest of which occurred in the Nile Delta city of Zagazig.

Sabahi's official campaign and the Egyptian Press Syndicate have reported similar irregularities during the vote that El-Sisi is expected to win by a landslide.

Officials have so far stated that reported violations will bear not impact on the integrity of the electoral process.

The Constitution Party said the government, security forces and the media were to blame for the people's perceived reluctance to cast their ballots, saying that cementing democracy and bolstering freedoms of expression and opinion were the only fruitful approach to boost turnout.

Sabahi also has the support leftists groups, including the Socialist Popular Alliance and the Revolutionary Socialists. He is also supported by the Karama Party, which he used to head, and his own Egyptian Popular Current.