Iranian President Hassan Rouhani has earned an emphatic vote of confidence and reformist partners secured surprise gains in parliament in early results from elections that could accelerate the Islamic Republic's emergence from years of isolation.

As of 0900 GMT on Sunday, latest results showed reformist candidates have taken all of the 30 seats in the capital Tehran, while Rouhani and his ally former president Hashemi Rafsanjani lead the winners in the assembly of experts, which is responsible for selecting the country's next supreme leader.

It remains unclear if the results in Iran will be replicated in other parts of the country. But a Reuters tally, based on official but partial results, also showed independents winning 44 seats, reformists 79, and hardliners 106 in the 290-seat parliament.

Iran's conservatives rally their supporters ahead of elections

A number of seats could be decided in run-offs in late April if no candidate wins the required 25 percent of votes cast. Eight of the initial winners were women.

A loosening of control by the anti-Western hardliners who currently dominate the parliament could strengthen Rouhani's hand to open Iran further to foreign trade and investment following last year's breakthrough nuclear deal.

"The people showed their power once again and gave more credibility and strength to their elected government," Rouhani said, adding he would work with anyone who won election to build a future for the industrialised, oil-exporting country.

The polls were seen by analysts as a potential turning point for Iran, where nearly 60 percent of its 80 million population is under 30 and eager to engage with the world following the lifting of most sanctions.

Nearly 33 million people voted to elect representatives to parliament and the country's highest clerical body.

Supporters of Rouhani, who promoted the nuclear deal, were pitted against hardliners close to Supreme Leader Ayatollah Ali Khamenei, who are wary of detente with Western countries.

Until now, the contest for this seat of clerical power was an unremarkable event, but not this time.

Because of Khamenei's health and age, 76, the new assembly members who serve eight-year terms are likely to choose his successor. The next leader could well be among those elected this week.

READ MORE: Opinion: A tale of two elections: Iran versus the US

Al Jazeera's Jonah Hull, reporting from Tehran, said while reformists and moderates were "expected to hold sway" in the capital, no one expected a countrywide landslide.

"The choices being made here broadly between conservatives and the moderate reformist bloc could well determine whether Iran moves towards greater tolerance, openness and much-needed economic reform, but in a system geared towards the ultimate power of religious conservatism, [where] old thinking and the status quo remain deeply entrenched," Hull said.

Moderate voter Behrooz Broum told Al Jazeera that he "would like to have a better economy, a better life, with friendship all over the world".

Yet, conservative support remained strong elsewhere. Zahra Ruzidar, a conservative voter, said she could not trust the United States.

"They keep insulting us. We came forward with honesty and negotiated an agreement, yet they keep threatening us. We are not afraid of threats," Ruzidar told Al Jazeera.

The hardline conservative camp is largely made up of loyalists of Rouhani's predecessor, Mahmoud Ahmadinejad, who, during his two terms in office, stoked tensions with the US and cracked down on internal dissidents.

In a bid to crowd them out, reformists have allied with moderate conservatives, many of whom split with the hardliners because of Ahmadinejad.

Reza Marashi, research director of the National Iranian American Council, said the results showed voters wanted change.

"Iranian voters delivered a strong message to the elite that political and social aspirations that have long been unmet neet to be addressed more robustly," he told Al Jazeera.

In a pre-election interview with Al Jazeera, Ghanbar Naderi, of the conservative Kayhan newspaper, however said that he was not expecting that things will change after the elections, even as he had predicted a reformist victory.

"They are all career politicians," he said, adding that it is time for older politicians to give way to the younger generation.

"We have great young minds in this country. But they are not given the chance."

READ MORE: Iran elections: Crucial polls a test for Rouhani

Reformists stormed to power with the 1997 election of President Mohammad Khatami, followed by the 2000 parliamentary elections that brought a reformist majority into parliament for the first time.

The movement pressed for an easing of Islamic social restrictions, greater public voice in politics, freedom of expression and better ties with the international community.

But that hold was broken in the next election in 2004, when reformist candidates were largely barred from running.

Ahmadinejad's election victory in 2005 sealed the movement's downfall. Reformists were all but shut out of politics for nearly a decade until Rouhani was elected.