Iran's defeated presidential candidate Mir-Hossein Mousavi has urged his supporters to continue with their protests, but in a peaceful and non-confrontational manner.
Mr Mousavi formally appealed against Iran's election result to the legislative body, the Guardian Council.
Thousands of supporters of Mahmoud Ahmadinejad have flooded onto the streets of Tehran for a rally addressed by the re-elected Iranian president.
Massive crowds of men and women waving Iranian flags and portraits of Mr Ahmadinejad packed central Tehran to listen to the president who won a second four-year term on Friday.
Cheers broke out as Mr Ahmadinejad opened his speech by paying tribute to the Iranian people and his supporters.
Earlier the incumbent leader, Mahmoud Ahmadinejad, said that the result of the president election was a blow to the ‘oppressive system’ ruling the world.
In his first press conference after winning the election, he also insisted that Tehran's controversial nuclear drive was an issue of the past.
Around 170 people have been arrested in Iran over the massive post-election protests and street riots in Tehran.
Ahmad Reza Radan, the city's deputy police chief, said ‘ten people, considered the masterminds of the rioting, have been arrested and more will be rounded up soon'.
Mr Radan said several people arrested were politicians who had judicial warrants issued against them.
The arrested reformists were members of Iran's leading reformist party Mosharekat.
A judiciary spokesman said the reformists had not been arrested but were summoned and 'warned not to increase tension'. They were later released, he said.
Meanwhile, police fired tear gas on a crowd of about 200 stone-throwing people as they protested in Tehran over President Ahmadinejad's disputed election win.
Angry supporters of defeated presidential candidate Mir Hossein Mousavi lobbed stones at policemen who fired back with tear gas to break up the demonstration.
Supreme Leader Ayatollah Ali Khamenei told Iranians to respect Mr Ahmadinejad's victory in a presidential election that his closest challenger described as a ‘dangerous charade’.
The reform groups had given their staunch backing to Mr Mousavi in Friday's disputed presidential poll.
Several of those arrested held senior government positions under two-time former reformist president Mohammad Khatami, who served from 1997 to 2005.
Among them were Behzad Nabavi, a former deputy parliament speaker, Mohsen Mirdamadi who headed the IIPF and parliament's foreign policy commission under Khatami, and Khatami's government spokesman Abdollah Ramezanzadeh.
The Islamic Iran Participation Front was founded in 1998, a year after Mr Khatami was elected.
The IIPF won more than 100 seats in the 290-seat parliament in the 2000 election.
The EU has expressed ‘concern about alleged irregularities during the election process and post-election violence’.
Germany's Foreign Minister Frank-Walter Steinmeier said Iran's crackdown on protestors was ‘unacceptable’.
Berlin also sought clarification about the election amid allegations of vote-rigging by Mir Hossein Mousavi.
US Secretary of State Hillary Clinton said the US was monitoring the outcome of the election closely and hoped the result reflected the will of the Iranian people.
However, Afghan President Hamid Karzai congratulated Mahmoud Ahmadinejad on his victory.
A statement quoting Mr Karzai said: ‘The selection of Dr Ahmadinejad with a definitive majority of the Iranian people's vote is a suitable selection for the continuous progress and welfare of the Iranian nation.’
President Karzai ‘congratulated this victory to the people of Iran as well’.
Other leading nations including Russia, Israel, and Arabic countries reacted with caution, but Afghanistan is keen to maintain good relations with its immediate neighbour.
Iran has close ethnic and religious ties with Afghanistan but the Islamic republic has been accused by Afghan and international military commanders of secretly supporting a rising Taliban insurgency against foreign forces here.