WASHINGTON - U.S. Vice President Joe Biden on Sunday cast doubt on the re-election of Iranian President Mahmoud Ahmadinejad, saying Tehran's actions against dissent suggest the results may not be clear-cut.

It sure looks like the way they're suppressing speech, the way they're suppressing crowds, the way in which people are being treated, that there's some real doubt, Biden told NBC's Meet the Press when asked if Ahmadinejad had won the vote.

I have doubts but we're going to withhold comment until we have a thorough review of the whole process and (see) how they react in the aftermath, he said.

Official election results gave Ahmadinejad nearly 63 percent of the vote and only 34 percent for his moderate opponent, Mirhossein Mousavi.

That's what they're announcing. We have to accept that for the time being. But there's an awful lot of question about how this election was run, Biden said.

But he cautioned: We don't have enough facts to make a firm judgment.

Mousavi dismissed Ahmadinejad's triumph as a dangerous charade while unrest erupted in Tehran and other cities in a display of political discontent.

Ahmadinejad's re-election could pose further challenges for U.S. President Barack Obama's hopes of dialogue with Iran and his outreach to the Muslim world.

Iran, under Ahmadinejad, has defied attempts by the United States and its allies to suspend its nuclear program, which the West claims to be an effort by Tehran to develop nuclear weapons. Iran denies the charge and says the program is aimed at nuclear energy.

After the vote, thousands of Mousavi's supporters took to the streets of the capital, chanting anti-government slogans and taunting riot police.

Police have detained more than 100 reformers, including the brother of former President Mohammad Khatami, a leading reformer said on Sunday. A police official confirmed some detentions.

In expressing his doubts, Biden pointed specifically to the vote count among Iran's cities, which he said account for 70 percent of the country's balloting but suggested that urban voters were not expected to turn out heavily for Ahmadinejad.

The idea he'd get 68 or whatever percent of the vote in a circumstance like that seems unlikely, the vice president said.

(Editing by Eric Walsh)