Voting began early in the day, with registered voters casting ballots at 63,000 polling centers countrywide.
"The business community, especially the private sector, is for Rouhani's re-election for the simple reason that we need continuity and consistency", said Cyrus Razzaghi, president of Ara Enterprise, a Tehran-based consultancy.
"A new record was set", he said, referring to presidential election turnout and noted that the result "showed increasing progress of Iranian nation". Millions of Iranians voted late.
Voters who spoke to The Associated Press from the cities of Bandar Abbas, Hamadan, Isfahan, Rashat, Shiraz and Tabriz also described crowded polling places.
On Friday, Iran did not allow foreign journalists and worldwide monitors to enter its territories to monitor the presidential polls. Millions of Iranians vo.
The country's Election Commission said Rouhani had obtained over 14.6 million votes, or approximately 56 per cent of the almost 26 million counted so far, suggesting he is on track for victory, Efe news reported.
So far more than 40 million votes have been counted of which 38.9 million are valid, the report added. The race was transformed by the April entry of Raisi, whose background spurred speculation he was being groomed as an eventual successor to Iran's ultimate arbiter, the 77-year-old Khamenei. Election officials extended voting hours at least three times.
So far he has secured 56.88 percent of the vote - a total of 22,796,468 votes out of the 40,076,729 votes cast.
"I am happy I could vote for Rouhani", said Zohreh Amini, a 21-year-old woman studying painting at Tehran Azad University.
Hei billed the deal as one that would thrust open the gates of economic opportunity, bring the country out of its isolation and create millions of jobs for Iranians.
Rouhani won 57% of the vote, or 23,549, 616 votes, said Interior Minister Abdolreza Rahmani Fazli. That puts turnout above 70%.
Iran's president is the second-most powerful figure within Iran's political system.
For ordinary Iranians, the election presents a stark choice between competing visions of the country. "I humbly bow my head down to you".
Iran's Supreme Leader Grand Ayatollah Ali Khamenei was among the first to cast his ballot and urged others to do the same.
But the president faces strong competition from Raisi who has made grounds by positioning himself as a defender of the poor and calling for a much tougher line with the West.
State TV offered its congratulations in a brief statement Saturday, based on vote tallies.
But his revolutionary rhetoric and efforts to win over working class voters with promises of increased handouts appear to have gained limited traction.
Rouhani's reforms have been modest and gradual, as Inskeep notes.
That hasn't stopped those at Rouhani rallies from shouting for the release of the house-arrested leaders of the 2009 Green Movement.
Iran's president oversees a vast state bureaucracy employing more than 2 million people, is charged with naming Cabinet members and other officials to key posts, and plays a significant role in shaping both domestic and foreign policy.
Six candidates had been vetted and approved by the Guardian Council to run in the election.
Ahmadi says the Interior Ministry hopes to have final results later Saturday.