TEHRAN, Iran - The one-year anniversary of Iran's disputed election passed quietly Saturday with little more than a subdued Internet appeal from opposition leaders for supporters to speak out on the Web against repression.

Fearing bloodshed and calculating that it would get them nothing, the movement's leaders called off a day of mass protests, reflecting their increasing powerlessness against the government's military muscle. Witnesses and the opposition reported a few isolated confrontations in the capital.

"We have to expand social networks, websites. These are our best means," said Mir Hossein Mousavi, a former prime minister who maintains he was robbed of the presidency through fraud in the June 12, 2009, election.

"These work like an army. This is our army against their military force," he said on his website, Kaleme.com.

The retreat from Iran's streets and university campuses to the Web is certain to be seen as a victory for the ruling hard-liners and for the armed forces that preserved their grip on power with a harsh crackdown on postelection protesters.

The anniversary passed with no signs of major disturbances or large gatherings.

Witnesses reported sporadic but minor clashes at Tehran's Azadi Square between a few dozen protesters and riot police swinging batons.

At Tehran's Sharif University of Technology, students scuffled with hard-liners and plainclothes paramilitary personnel on campus, according to Mousavi's website. "Liar, liar," students chanted in a denunciation of President Mahmoud Ahmadinejad.

Security forces arrested a political ally of Mousavi, Davoud Roshani, and labor union activist Reza Shahabi, Kaleme.com reported.

Authorities were also seen taking one person away near the entrance of Tehran University, another witness said.

In some Tehran neighborhoods after nightfall, people went to their rooftops and shouted "Allahu akbar" - "God is great" - reprising a cry of protest from last year.