Tens of thousands of opposition and pro-government demonstrators have held rallies in the Iranian capital, raising fears of possible clashes.
Thousands of people gathered at a government-organised rally in Tehran's central Vali Asr square on Tuesday, while a similar-sized demonstration was held by opposition supporters in the city's north.
State television footage showed a crowd of thousands of flag-waving protesters at the pro-government rally, while the media was banned from filming the opposition protests.
"They are two completely different events," Al Jazeera's Teymoor Nabili, who watched both rallies, said.
"The Ahmadinejad rally in the south was a much more organised affair - they had built a little platform and there were speakers there."
He said by contrast the smaller, anti-government rally, taking place just six or seven kilometres away, was "almost completely silent".
"They're planning to start chanting at 10pm tonight [17:30 GMT]," he said.
Pro-government demonstrators have demanded the government crack down on the opposition, while their anti-government rivals have protested that their votes were "stolen" in the presidential election, which saw Mahmoud Ahmadinejad, the incumbent, win a landslide victory over his rival Mir Hossein Mousavi.
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Seven people were killed on the fringes of a massive opposition rally a day earlier.
Mossavi had urged his supporters to stay away from Tuesday's rally amid fears of further clashes.
In a message posted on his website, he asked his supporters to "exercise self-restraint".
Sadegh Zibakalam, an Iranian political analyst, said that the government had arranged its protest on Tuesday as a response to the anti-government movement.
"The government doesn't want to appear as being too soft - that's why they called this rally today and asked its supporters to come to the square where Mousavi's supporters had decided to gather," he told Al Jazeera.
"By arranging these crowds the government is making two points. It wants to demonstrate that it is firm in dealing with this crisis, [and] on the other hand they have been called [on] by the pro-government crowd to crack down.
"In a sense it is a justification for the seven people who were killed last night."
The rallies came just hours after Iran's powerful Guardian Council said it could order a partial vote recount if it found irregularities.
The legislative body has ruled out annulling the disputed poll, but the Council's move appears to be a first concession by authorities to the protest movement.
A spokesman for the Council, a constitutional watchdog formed by a 12-member group of clerics and Islamic law experts, said only that it was "ready to recount the disputed ballot boxes claimed by some candidates, in the presence of their representatives".
"It is possible that there may be some changes in the tally after the recount," Abbasali Kadkhodai, a Council spokesman said.
"Based on the law, the demand of those candidates for the cancellation of the vote, this cannot be considered," he told state television.
In Washington, Barack Obama, the US president, said he believed "people's voices should be heard and not suppressed" but also said that he did not want to be seen as "meddling" in Iranian internal affairs, given the history between the two countries.
Iran has grown increasingly sensitive to how the world views the heightened tensions and has subsequently restricted reporting by journalists working for foreign media.
Iranian state television said earlier that the "main agents" in post-election unrest had been arrested while carrying explosives and guns.
Gholamhossein Mohseni-Ejei, Iran's intelligence minister, said his ministry was chasing two categories of people seeking to create instability in Iran, one of them backed from abroad.
Despite the upheaval in Iran, Ahmadinejad travelled to Russia for a meeting of the Shanghai Co-operation Organisation, his first foreign trip since official results showed he had secured a second four-year term.