Vladimir Putin's crackdown against dissent has seen 28 people arrested over the past year. But their cause is not forgotten

In a black-and-white photo taken in court the day she was charged, Alexandra Dukhanina looks like a young Audrey Hepburn, with a side-swept fringe and coy smile. Two police officers loom behind her. A nearby cage stands empty.

That was one of the last times Dukhanina, 19, was seen in public. For nearly a year, she has been under house arrest, confined to a flat in western Moscow, for taking part in a protest against President Vladimir Putin that turned violent on the eve of his inauguration on 7 May last year.

The most insidious aspect of the crackdown that followed, activists say, is the slow but steady arrest of some who took part in the 6 May protest. In all, 28 have been arrested; most recently, the 27-year-old Alexey Gaskarov, last week.

Some were arrested in their homes. Others, like Dukhanina, were nabbed on the street. Some are behind bars and awaiting trial. Others, like Dukhanina, are under house arrest, completely cut off from the outside world.

On Monday, the first anniversary of the protest, the Russian opposition, although cowed by Putin's crackdown and the re-emergence of political apathy among the general population, will take to the streets calling for the release of the 6 May political prisoners.

They will gather at the same site – Bolotnaya Square – where clashes broke out between riot police and protesters amid a wave of passionate demonstrations that swept Moscow for months as Putin planned to return to the presidency.

The authorities accuse Dukhanina and 27 others of organising the unrest. Opposition activists, in turn, accuse Russia's notorious riot police of provoking the disorder and say the Kremlin has seized on the unrest to unleash a far-reaching crackdown designed to spread fear among those who would dare protest against Putin.

The fear has worked. Subsequent protests have brought out a tiny fraction of the tens of thousands who took to Moscow's streets last year. The avid political debate that erupted among average Muscovites around Russia's presidential election has largely faded into the background. Yet those who have remained committed have become ever more angry.

"They've been trying to scare us for all of the past year," said Ilya Yashin, an opposition leader. "Those who got scared have gone back into their homes, to talking about things in the kitchen. Those who have remained have got more and more angry. Now the atmosphere in the air, I would say, has the smell of civil war, though it is a cold civil war for now."

Dukhanina was among the first to be arrested. She was briefly detained on 6 May last year, along with hundreds of others, amid an hours-long standoff between protesters and police. Photographs from the day show her being dragged away by a camouflaged riot police officer, her hands clawing at his arm holding her in a tight headlock. She was released later that day.

Then, three weeks later, police detained her as she was sitting in a park with friends after a poetry reading at Mayakovsky Square in Moscow, long a favoured site of political gatherings.

Three days later, a judge said she would be charged with mass unrest and harming a representative of the state, arguing that she had hurled rocks, bottles and pieces of asphalt at riot police. She was ordered into house arrest.

Since last May, Dukhanina, and the others under house arrest, have been cut off from contact with all but their lawyers. They cannot use the telephone or the internet, nor receive or send letters. "She's completely cut off from society," said Dukhanina's lawyer, Dmitry Yefremov.

A Moscow court is expected to hear the case against those charged during a mass political trial this summer. The 28 defendants have nothing in common – in most cases, they do not know each other – aside from separately attending the protest.

Already reeling from a series of laws clamping down on the right to protest and on the rights of non-governmental organisations, as well as the trial against the main opposition leader Alexey Navalny, activists have begun to warn that could be the last straw.

"Putin has done a lot to ensure confrontation," said Yashin. "His decisions, his laws, his rhetoric, don't unite society, but divide people. It's very dangerous for the country, because it can bring the country to civil war.

"I hope it won't happen. The taste for blood in Russia is exhausted. We must do everything to avoid a revolt. But anything can happen."