Left Front leader Sergei Udaltsov has gone on hunger strike in a Moscow prison as his wife Anastasiya carries on organising the pro-democracy campaign

It is 10am and the tatty apartment blocks of southern Moscow are still shrouded in winter darkness as a slender young woman hurries towards the metro.

Black-haired, in jeans and a thin leather jacket, this is Anastasiya Udaltsova, one of the leaders of the civil protests that have swept across Russia, bringing tens of thousands of demonstrators on to the streets to express their disgust at rigged elections earlier this month.

Udaltsova, 33, is rushing to meet friends to drum up support for a new rally that will take place in Moscow on Saturday. She and the other organisers – including the hugely popular anti-corruption blogger Alexei Navalny and the veteran oppositionist Boris Nemtsov – are now exposed to the full hostile glare of the state.

Her husband, also a protest leader, is in jail and has embarked on a hunger strike in protest at the allegedly trumped-up charges, while Udaltsova is left alone to care for their two children.

On 10 December an estimated 40,000 people gathered in the centre of Moscow in the largest demonstration against the rule of Vladimir Putin after videos of ballot-stuffing and other falsifications by the pro-Kremlin United Russia party spread across the internet.

The event was peaceful; the Kremlin evidently took fright after police inflamed opposition anger when they broke up an earlier protest the day after the vote. But the future remains uncertain. "When the leader of our country says a demonstrator can be bashed round the head with a truncheon, then who knows what to expect," says Udaltsova, referring to a typically salty comment made by Putin, the prime minister, last year.

In his annual phone-in show on Thursday, Putin expressed his contempt for the protesters, saying they were paid to attend. He also claimed he thought the white ribbons they wear to show solidarity looked like condoms.

"These are the words of a tyrant, not a potential president," says Udaltsova, who hopes that protests will continue right up to the presidential election in March, when Putin hopes to return to the Kremlin. "People are rising up," she adds. "They won't stand for these things any more, for the lack of freedom." United Russia was awarded almost 50% of the parliamentary vote, an estimated 15% higher than its real share.

For the protest organisers, the price of dissent can be high. Udaltsova fell into her leadership role by accident: her husband, Sergei Udaltsov, was arrested on 4 December, the day of the parliamentary elections, and given five days' jail for "resisting officers' recommendations to cross the road in the correct place", a claim he says is nonsense.

It was part of a campaign of persecution that has left Udaltsova and her husband nervous wrecks. Udaltsov, 34, is the leader of Left Front, a radical anti-Kremlin group that joined forces with a wide spectrum of groups over the current protests. He has spent 86 days in jail since November 2010 on various administrative misdemeanours.

"These cases are fabricated as a deliberate obstacle to prevent Sergei from exercising his constitutional right to free political expression," says Nikolai Polozov, one of his lawyers.

Just as he was about to be released after his punishment for jaywalking, Udaltsov was issued with a 15-day sentence for allegedly leaving a hospital where he was being treated during yet another detention in October. An estimated 20 officers in riot helmets were sent to collect him, along with plainclothes operatives from the Federal Security Service.

"They wanted to make sure he couldn't get to the protests," explains Udaltsova. "It's incredible. The security services escort him back and forth in a convoy of cars as if he is Russia's criminal No 1."

Now her husband is being held at a spetspriyomnik (special detention centre) in a grim Moscow suburb, a pitted two-storey building surrounded by 3m fences topped with rolls of razor wire. Navalny, the blogger, and Ilya Yashin, a young activist with the Solidarnost group, are detained in the same building after being given 15-day sentences for taking part in a demonstration. Photographs of the jail's interior published last week show the corner of a cell infested with cockroaches and the unshaven inmates standing between steel bunk beds.

Furious at his treatment, Udaltsov has been on hunger strike since he was arrested. Udaltsova says he eats no food and drinks nothing at the detention centre, only sipping a little water and accepting a drip to stave off complete dehydration when he is periodically taken to hospital. "I wish he would start eating, of course," she says. "But he is desperate, and I understand his motives."

Her husband's ordeal has put a huge strain on the family, especially her sons, aged 11 and seven. "They miss their father," she says. "They think it's all so bad that Santa won't come to Russia because of Putin."

Russia's courts have ignored all appeals against Udaltsov's detention. His allies can only hope for support from international bodies. Last week Amnesty International called for his immediate release. Another of Udaltsov's lawyers, Violetta Volkova, has applied to the European Court of Human Rights in Strasbourg with a detailed list of procedural violations.

Volkova says she fears for her client's life. "The neglect is a form of torture. Sergei needs to be permanently in hospital while he's on hunger strike. There is no qualified doctor at the spetspriyomnik. A prison guard checks on him now and then, but how would he know when someone's kidneys are breaking down?"

She adds: "I think the authorities would be very happy for him to die. All that's saved him so far is that nobody wants it to happen on their shift."

Udaltsova, who normally works as a press officer for Left Front, says: "It's hard for me on my own, shouldering all Sergei's tasks. But we must keep up the fight. It will be a disaster if Putin gets back in the president's chair."

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