TEHRAN: Iranians voted Friday in a major test for President Hassan Rouhani, a moderate who hopes to curb conservative dominance and provide an opening for domestic reforms after a nuclear deal with world powers.

The Islamic republic's ultimate authority, supreme leader Ayatollah Ali Khamenei, was among the first to cast a ballot and he urged 55million eligible voters to do so "quickly, as it's both a duty and a right".

As well as picking 290 members of parliament, the electorate will also vote in a second election to select the Assembly of Experts, a powerful committee of 88 clerics that monitors Khamenei's work.

The polls are especially important as they come just one month after sanctions were lifted under the nuclear accord and the vote's outcome will be seen as a de-facto referendum on Rouhani's administration.

Known as the "diplomat sheikh" on account of his clerical credentials and willingness to negotiate, Rouhani was the driving force behind the nuclear deal, which he delivered despite political pressure at home.

The agreement raised hopes in Iran but the economy remains in the doldrums after a decade of sanctions that prompted a deep recession followed by high inflation that eroded the public's purchasing power.

A pro-government coalition of moderate and reformist candidates called "The List of Hope" is representing the president's ambitions in the polls.

Lawmakers are elected for four years but the assembly has eight-year terms. Should Khamenei, who is 76, die during that time its members would pick his successor.

Voting began at 8:00 am local time and was due to end at 6pm, although officials say polling stations could stay open longer if there are queues.

"We have enemies"

Observers will be closely watching turnout figures, with higher voter participation expected to benefit moderates and reformers.

Khamenei smiled warmly as he spoke to electoral officials and presented his identity documents before receiving his ballot paper which he posted in a sealed box at 8.09 am.

"Everyone must vote, those who love Iran, those who like the Islamic Republic, those who love the grandeur and glory of Iran," he said.

Having backed Rouhani in the nuclear talks with the United States, the Islamic republic's bete noire, Khamenei has since warned against economic and cultural "infiltration" from the US.

"We have enemies. Elections should be such that they make the enemy disappointed. We must vote with insight and open eyes," he said.

Iranians could choose to endorse the international outreach started by Rouhani or deliver a stinging rebuke instead.

If voters support the pro-Rouhani list the president could swing the balance of power in parliament and have a chance of passing reforms through legislation on which he has so far been blocked.

After voting in Tehran, the 67-year-old president pledged to protect the integrity of the elections.

"The government sees the vote of as an immense mark of trust," Rouhani said. "I assure people that the government, the interior ministry, the supervisory committees and the entire system all do their best to hold legitimate and healthy elections." Atefeh Yousefi, 38, took recent official encouragement to vote to heart.

"I expect the situation of the country to improve through reforms," she told AFP while waiting in line at a polling station in Tehran, adding that she regretted not voting in past elections.

Reformists versus conservatives

The one-week official campaign for the parliamentary election was largely overshadowed by controversies over who was allowed to run for office.

The exclusion of thousands of candidates ─ reformists said they were worst hit, with the barring of their most prominent faces leaving them with untested hopefuls ─ has raised concerns over turnout.

A total of 4,844 candidates, about 10 per cent of whom are women, are standing in the parliamentary election. Only 159 clerics ─ a fifth of the applicants ─ are seeking a place on the Assembly of Experts.

The pro-Rouhani List of Hope is headed by Mohammad Reza Aref, a former vice president in the 1997-2005 two-term government of reformist president Mohammad Khatami.

“If we win, the path becomes much smoother,” Aref told AFP, saying a similar result as Rouhani's victory of 2013 ─ in which he won in a first round with 51 percent of the vote ─ could usher in prosperity.

"Hopefully once we win a majority our first step will be an economic boom in the next parliament," he said.

The main conservative faction in the parliamentary polls is headed by Gholam-Ali Hadad Adel, a former parliament speaker, whose daughter is married to one of supreme leader Khamenei's sons.

"I'm optimistic," Hadad Adel said.

"I'm sure the Iranian nation... with their well-known insight, will continue the path of the Imam and the leadership," he said, in a nod to the Islamic republic's founder Ayatollah Ruhollah Khomeini, and his successor, Khamenei.

Results from outside Tehran were expected within 24 hours but the vote tally in the capital, which has a population of 12 million and is electing 30 lawmakers, will take three days.