Riot police in front of cloud of tear gas as supporters of Mir Hossein Mousavi clash with police in Tehran, 13 Jun 2009

Iranian authorities have detained more than 100 people connected to opposition political parties while riot police worked to contain continuing protests against the landslide reelection victory of President Mahmoud Ahmadinejad.

Reformists said Sunday one of those arrested is a brother of Iran's former reformist President Mohammad Khatami. They said some activists were released after being detained.

Also Sunday, reformist presidential candidate Mir Hossein Mousavi appealed to Iran's powerful Guardian Council of Islamic clerics for the cancellation of election results.

Mr. Mousavi has blamed his defeat on what he says was government voter fraud. President Ahmadinejad has said the election was free and fair.

Mr. Mousavi urged his supporters to continue protesting in a peaceful and legal manner. Pro-Mousavi activists held a second day of protests in Tehran Sunday, setting fires in the streets and fighting with police.

Hossein Mousavi shows ink on his finger as proof of casting his vote in the Iranian presidential election

Meanwhile, tens of thousands of supporters of President Ahmadinejad celebrated in the capital.

U.S. Vice President Joe Biden told U.S. network NBC Sunday he has doubts about the election's outcome.

But, he refrained from saying whether the Obama administration accepts it.

Official results showed Mr. Ahmadinejad won 63 percent of the vote, compared to 34 percent for Mr. Mousavi, his main rival.

Mr. Mousavi has not been seen in public since Friday's election.

At a Sunday news conference, Iran's president said his margin of victory in the disputed election was so big that it cannot be questioned.

Mr. Ahmadinejad said the protests against the election's results were " not important" and likened those complaining about the election to football (soccer) fans who are disappointed when their team loses. He said it is natural for police to fine such people when they violate traffic rules.

Iran's president also said the international controversy over Iran's nuclear program is something that belongs in the past. Some Western nations accuse Iran of trying to develop nuclear weapons under cover of a civilian energy program, a charge Tehran denies.

Iran's supreme leader, Ayatollah Ali Khamenei, welcomed Mr. Ahmadinejad's apparent landslide victory and urged the country to unite behind the president.