Russian President Vladimir Putin on Saturday asked his people to repulse terrorism and announced a three-pronged approach in strengthening security of the multiethnic nation.

In an address to the nation following the Beslan hostage tragedy, in which 322 people died, he said, "Several times we have faced crisis situations, rebellions and terror acts, but what happened this time is inhuman, unprecedented brutal crime of the terrorists.

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"This is not a challenge to the president or Parliament, it is a challenge to Russia... This is an aggression on our country."

Putin blamed the disintegration of the USSR and collapse of the Soviet security machinery for modern Russia's inability to cope with "intervention of the international terrorism".

He said international terrorism wanted "to disintegrate the unity of the country".

The president announced introduction of a system of interaction and coordination of the whole defence and security structures in the North Caucasus, and installation of anti-crisis governance, including functioning of law enforcement bodies on new principles.

He, however, said that it would be done strictly within the framework of the constitution.

"The terrorists think... they can scare us with their cruelty, that they will be able to paralyse our will," he said.

"We are faced with a choice -- either to fight them off or to agree with their claims," he said.

Later, Putin declared national mourning on September 6 and 7 in the memory of hundreds of the victims.

Flags will fly at half-mast and all the entertainment programmes will be cancelled throughout the country, the Kremlin press office said.