Campaigners who lost their relatives in the Beslan school siege are due to be put on trial in Russia on Monday after prosecutors charged them with extremism for blaming President Vladimir Putin’s regime for the 2004 massacre.

The case, brought by prosecutors in the north Caucasus region of Ingushetia, was the latest example of Russian authorities trying to stamp out criticism with a recently toughened extremism law, observers said.

Ever since Mr Putin broadened the definition of extremist activity last year to include “slander of public officials” and “humiliating national pride”, officials have used it to launch investigations into journalists, human rights activists and opposition leaders, including Garry Kasparov, the former world chess champion.

“The authorities are doing all they can to close us down,” said Ella Kesayeva, co-chairwoman of the Voice of Beslan movement, which last summer filed a case against Russia in the European Court of Human Rights for failing to investigate the massacre properly. The movement is trying to conduct its own investigation.

Critics such as Ms Kesayeva’s group say evidence shows law enforcement agencies botched the school siege in Beslan, North Ossetia, where Chechen terrorists held more than 1,000 people hostage. The siege ended with more than 330 people dead – the majority children – after special forces stormed the school.

“If the court rules in the prosecutors’ favour, they can bring criminal charges against us if we don’t close down,” said Ms Kesayeva. “We are victims. We should be on rehabilitation programmes, not being persecuted.”

A spokesperson for the Ingush prosecutors’ office said the outcome of the extremism case would depend on the judge’s ruling, which he said could merely order the group to pull publications from the web.

Prosecutors are bringing the case over a number of publications, including an appeal to world leaders in November 2005 that accused Mr Putin’s regime of “aiding terrorism” and said he was using an official investigation to cover up the use of tanks and heavy firepower on the school.

Dmitry Peskov, the Kremlin’s deputy press secretary, said he was not aware of the details of the case and said the law should not be used to muzzle critics. But he said: “Each case needs to be examined individually.”