In 2005, the ministry recorded 958 cases of people disappearing and not being found, but in 2006 that rose to 3,178. The remains of hundreds more missing people were only discovered months or years after they were put on the search list.

Commentators say law enforcement agencies across the country have focused their resources on fighting terrorism, fraud and organised crime, while neglecting searches for the disappeared. 'We have reached a catastrophic situation with people going missing without trace,' said Vladimir Ovchinsky, a retired police major-general and former head of Interpol in Russia.

In Nizhny Tagil, Ms Kuzmina and her relatives were not alone as they searched for her sister. From 2002 to 2006 a series of girls and young women went missing in ones and twos from the city, a sprawl of low-rise apartment blocks and belching smokestacks.

Relatives informed police and posted signs in the street pleading for information.

But only in the past few months has the fate of Irina Kuzmina and others become clear: up to 30 female victims were kidnapped, raped and finally strangled after they refused a gang's demands to work for a handful of dollars a night as prostitutes in a city brothel called Prestige. The discovery of the women's corpses - several years after many of them went missing - and the arrest in February of eight men accused of their murder, shocked many Russians.

So far 14 bodies have been identified. Eight were found in a mass grave stumbled on by a dog-walker near a village about 65km away. The rest were dumped individually or in pairs near the city. Prosecutors said unidentified body parts also found in the graves could add up to another 15 people.

Police in the city of 400,000 had not linked the disappearances. Relatives who reported loved ones missing up to four years before their bodies were found complained that search efforts were half-hearted or non-existent. 'The police just made out they were too busy to help us,' said Dima Vishnyakov, whose sister Natasha, 23, was also abducted and killed by the gang. 'They said had better things to do.'

Officers in Nizhny Tagil deny incompetence, claiming there was nothing to connect the disappearances at the time, and that many families never reported the women as missing.

Officials at the federal interior ministry's Moscow headquarters insist that, long term, the rate of disappearances is not on the rise. 'The statistics have a wave-like character that fluctuates,' the head of the criminal search directorate, Yelena Zelembinskaya, said. 'It just so happens there was a peak in 2006.'

However, critics say the number of people who have disappeared in the past 15 years is expected to hit 50,000 this year, the population of a small town. That figure is also the number of active missing persons cases in the US, which has twice Russia's population.

Many of the missing in Russia are thought to be victims of paedophiles, human traffickers or extortionists who force their victims to sign over property such as apartments before they are killed and their corpses hidden.

Experts say switched priorities by authorities are partly to blame. After the Beslan school siege in 2004, President Vladimir Putin increased budget funding to the federal security service and the interior ministry to fight extremists. More recently police have led a high-profile, Kremlin-backed anti-corruption drive that saw several regional leaders ousted from their posts.

'The police are operating on the principle 'no body, no problem',' said Mr Ovchinsky. 'Searching for someone takes time and effort and often ends with a corpse, which worsens the crime statistics. So they don't bother.'

Police attitudes to prostitution can make young females especially vulnerable. 'A lot of the time they see the women involved as the people at fault, and not the pimps who control them,' said Afsona Kadyrova of Angel Coalition, a Moscow-based group fighting human trafficking.

The girls and young women who disappeared in Nizhny Tagil were allegedly kidnapped by two brothers and their accomplices, who murdered them after they refused to work in their brothel, or after they tried to escape. In order to lure them to the brothel the gang used an attractive young man called Mark Kustovsky, dubbed 'The Charmer' by detectives.

Irina Kuzmina met him in November 2004 but failed to come home after telling her sister one evening she was going to meet Kustovksy. She was never heard of again. Her body was only found last year and 'The Charmer' is one of the men to go on trial for the murders.

Asked about the police response when Irina did not return home, Ms Kuzmina shrugged her shoulders. 'They didn't seem interested when my older sister and I reported her missing.'