The informed source told Tasnim that the higher-than-expected turnout in the elections has convinced the Interior Ministry to extend the voting time until 8 pm local time all around the country.
Polling stations opened at 8 am on Friday morning and were scheduled to close after 10 hours.
Around 61 million Iranian people are eligible to vote, including 3.5 million first-time voters.
The elections are held in around 60,000 polling stations across Iran.
Some 250,000 forces have been tasked with ensuring the security of elections on Friday.
There are currently 290 seats in the Iranian Parliament, known as Majlis, elected by direct vote of people in nationwide elections for four years.
The Assembly of Experts is a high-ranking body that elects and oversees the activities of the Leader of the Islamic Revolution.
Members of the assembly are directly elected to office by people for an eight-year term. It holds biannual meetings to appoint a new chairman.