TEHRAN, (Reuters) – Iran’s Revolutionary Guards warned the opposition on Saturday, the first anniversary of a disputed presidential election, that they would crack down on any attempts to create a “security crisis”.

Authorities had banned an opposition rally planned for Saturday, and reformist leaders had told their supporters to stay home, fearing for people’s lives in any crackdown.

There was a heavy security presence on Tehran’s squares, and the only sign of opposition activity was the countless cries of “Allahu Akbar” (God is Greatest) heard from rooftops on Friday night — a move urged by opposition figures in exile. “Any revival of street protests is unlikely. But if the sedition movement creates a security crisis, we will confront them with full force,” said senior Guards commander Reza Farzaneh, according to the Javan newspaper.

Last year’s post-election street protests, the worst unrest since the Islamic republic was founded in 1979, were put down violently by the Guards. Mass detentions and trials followed. Two people were hanged and scores of detainees remain in jail.

The opposition says the vote was rigged to secure the re-election of the hardline president, Mahmoud Ahmadinejad.

The authorities deny the accusations, saying they are part of a Western plot to overthrow the Islamic system, and have repeatedly said they will prevent any revival of the protests.

Many Iranians critical of the government now seem unwilling to risk violence or arrest with displays of dissent, and doubts have grown over the effectiveness of the reformists’ leaders. “What have the opposition leaders been able do for my friends who are still in jail?” said Mohammad Sefati, a 25-year-old literature student in the city of Mashhad. “I am a backer of the reform movement. But what can we do without any leadership?”

Defeated presidential candidate Mirhossein Mousavi says the movement is alive, but his campaign is fading as many Iranians feel the former prime minister lacks the political courage to confront the establishment from which he sprang.

At least a dozen pro-reform publications and most opposition websites have been blocked since the vote, making it hard for the opposition leaders to communicate with the public.

The last major opposition protest in December led to clashes with security forces in which eight demonstrators were killed.

Since last week, the government has intensified its clampdown, arresting dozens of activists, journalists and students.

Narges Mohamadi, a close aide to Iran’s 2003 Nobel Peace Prize winner Shirin Ebadi, was arrested on Thursday, Ebadi’s Defenders of Human Rights Center said.

The United States said on Friday it was working to convince members of the U.N. Human Rights Council to voice solidarity with the victims of the post-vote violence and repression.

On Wednesday, the U.N. Security Council passed a fourth set of sanctions intended to curb Iran’s nuclear programme, which the West fears is a cover for nuclear weapons development.

Iran, the world’s fifth largest crude oil exporter, insists it needs nuclear technology to generate power.

Authorities have been trying to reassure Iranians that the new sanctions will have no more impact than previous ones, which have failed to cripple the economy. But ordinary Iranians seem more concerned about low salaries, high inflation and increasing unemployment.