Iranians went to about 15,000 polling stations across 21 provinces to cast their ballots in runoff parliamentary elections on Friday.
The second round saw a contest among 136 candidates who had launched one-week campaigns in the hope of grabbing one of the 68 remaining seats of the 290-member parliament.
The voting began at 8 a.m. in 121 cities and was to end at 6 p.m. local time.
But Interior Minister Abdolreza Rahmani Fazli, whose body is in charge of conducting elections, said in a press conference on Friday that the period was extended by one hour.
The minister urged around 17 million eligible people to vote early in the day, so the results could be announced by Saturday morning.
"If there is no need to extend the period anymore, the returns will be released by 8 a.m. tomorrow," IRNA reported him as saying.
The first round of the polls was held on February 26 and 222 candidates were elected. The fate of the vacant seats in 55 constituencies, where nobody could get at least 25% of the votes, was to be decided in the Friday runoffs.
Unlike the primary polls, there are no minimum requirements for winning the runoffs and a simple majority of votes will help secure a parliamentary seat.