Despite nine weeks of savage repression since Iran’s hotly disputed presidential election, opponents of the regime refuse to accept defeat. They accuse the Government of torturing political detainees. They spread samizdat DVDs, use paintball guns to obliterate government posters, and attack government websites.

Mehdi Karroubi, one of the defeated presidential candidates, kept up the public pressure this week by claiming that male and female detainees have been raped in the Evin and Kahrizak prisons in Tehran, and that political prisoners were being tortured to death.

“We observe that in an Islamic country some young people are beaten to death just for chanting slogans,” Mr Karoubi wrote on his website.

Other detainees “were forced to take off their clothes. Then they were made to go on their hands and knees and were ridden [by prison guards]. Or the prison authorities put them on top of each other while they were naked... Do such treatments conform with Islam, which is a religion of mercy?”

Mr Karoubi’s allegations, which are supported by Western human rights organisations, seemed designed to deepen rifts within the conservative establishment over the way detainees have been treated.

They certainly appeared to strike a nerve. The regime has denounced them as baseless, and demanded Mr Karoubi produce proof. Ayatollah Ahmad Khatami, a hardline cleric, used his sermon at Friday prayers to demand that Mr Karoubi be prosecuted. He said that the accusations were “full of libel, a total slander against the Islamic system” that helped Iran’s enemies.

With the security forces brutally suppressing any street demonstrations, grassroots activists are adopting subtler methods of resisting a regime that they consider illegitimate.

They still chant “Allahu Akbar” (God is greatest) from the rooftops every night, and write anti-regime slogans on banknotes, but they are also daubing graffiti (“Death to basiji”, “Death to the dictator”) on walls across the capital and using paintball guns to obliterate posters of Ayatollah Ali Khamenei, the Supreme Leader, with green paint. Sometimes they simply paint a black X across his portrait.

Thousands of samidzat DVDs are discreetly distributed in cafes, restaurant and tea houses, and through networks of friends and relatives. They document the regime’s crimes, show protesters being beaten up, and focus on the faces of the the basiji militiamen administering the beatings so they can be identified.

At football matches, religious ceremonies or anywhere that large crowds gather, small groups start chanting and others join in. “It has reached such a stage that the Government is trying not to show sports events live. When they do they censor the noise and try not to show the spectators,” said one reliable source in Tehran.

The opposition plans to step up its attacks on government websites, and to create huge traffic jams outside government offices to prevent employees getting to work. From next week it also plans to paralyse the heavily used rail system on selected days by holding doors open, pulling emergency brakes and other such actions.

There are still periodic street demonstrations. On Wednesday thousands gathered outside Tehran’s huge, labarythine bazaar. “When the police attacked we were able to run into the maze of the bazaar and its surrounding streets only to reappear at a different place to continue the protest,” one participant told The Times. Sympathetic merchants sheltered the protesters, and on at least one occasion beat pursuing basiji.

One prominent activist, Mohsen Armin, has issued a pre-emptive denial of any future “confession” he may make he is arrested and tortured. He had received no foreign money or assistance, he wrote on his website. He had not called for a revolution, just for the constitution to be respected. “If, in jail and under pressure, I say something against what I have said, be sure that it is not my true belief.”

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