The Russian presidential envoy to Chechnya has said lax security standards allowed suicide attackers to bomb a government building in Grozny, killing 55 people.

The rebels are trying to bring the Chechen people down to its knees, but they will not succeed Russia's human rights envoy for Chechnya, Abdul-Khakim Sultygov

"Many people are guilty of negligence, from the army ranks to responsible, high-ranking figures," said Viktor Kazantsev.

Russian officials said on Saturday that the bombers involved had been wearing Russian army uniforms and carrying Russian security passes when they entered the headquarters of the Russian-backed government.

Chechen separatist rebels have claimed responsibility for the explosion which injured at least 120 people.

Rescuers are still searching through the rubble for survivors. Five people were pulled alive from the rubble on Friday night but there are fears that the death toll may rise.

Condolences

Former Chechen President Aslan Maskhadov, the Chechen political leader ousted by Russia three years ago, has denied any involvement in Friday's bombings.

Mr Maskhadov issued a statement of condolence on Saturday saying the attack was wrong.

"I speak to those who have decided to take the path of self-sacrifice after suffering painful experiences and losses," he said in the statement carried on rebel websites.

"I understand you but I cannot support you.

"The Kremlin uses any means to link Chechens to international terrorism. Our task is not to prove them right."

'Inhuman attack'

However, Russia's human rights envoy for Chechnya, Abdul-Khakim Sultygov, told Russian news agency Interfax that the separatists were attempting to destroy the peace process.

Correspondents say Putin's response is likely to be swift, and tough

"The extremists are trying hard to achieve the state of emergency in Chechnya and to thwart the referendum on the Chechen constitution," he said.

"The rebels are trying to bring the Chechen people down to its knees, but they will not succeed."

Russian President Vladimir Putin described the attack - the worst suicide bombing ever witnessed in Russia - as "inhuman", accusing the rebels of waging war against their own people.

Peace plans

Friday's attack marks the rebels' biggest operation since the taking of a packed Moscow theatre in October.

The BBC's Steve Rosenberg in Moscow says the president's response is likely to be swift, and tough.

However he adds that it is unclear what impact the incident will have on the Kremlin's proposed peace initiative for the region - which includes holding a referendum early next year on a new constitution.

The referendum's supporters hope it will help bring stability to a region ravaged by conflict for the past decade.