Russian newspapers and some politicians have questioned how a few dozen militants could take so many hostages and then stand up to hundreds of Russian troops during a grisly raid that lasted for more than six hours, killed at least 322 people and maimed hundreds more.

The volatile Caucasus region is notorious for its tight road security, because of a decade of warfare in separatist Chechnya and flaring conflicts in other nearby multi-ethnic republics.

But the Russia media is filled with reports of the road police letting just about anyone pass through in return for bribes.

The head of the North Ossetian security service said that he was certain now that the guerrillas had located their point of attack well in advance and had not simply rushed into the school on Wednesday, the first day of the academic year, on the spur of the moment.

"We found a large amount of explosives and mines and their number says that this attack was planned in advance," security chief Valery Andreyev was quoted as saying by Interfax.

"The armaments were hidden on the school grounds," he said.

He gave no other details but other sources fleshed out the story.

One unnamed source was quoted as saying the militants first scouted out two other schools before settling on School Number One -- the main one in Beslan -- because it was undergoing major reconstruction work over the summer.

The school needed everything, including a new floor for its gym.

"It looks like they settled on a school that needed renovation ... and which needed a new floor set for its gym," ITAR-TASS quoted an official as saying.

The hostage-takers herded their captives into the gym on September 1 and kept them there for three days without food or water, suffocating in overwhelming humidity and heat and surrounded by home-made explosives.

"Some of the teachers (who were taken hostage) recognized a few of the rebels because they worked on the school construction project... At at that point they were working on the safes," Ismel Shaov, spokesman for the North Ossetian interior ministry, told AFP.

"They brought in a lot of explosives while they were doing their work."

One official told news agencies the hostage-takers had settled on the building in July.

They posed as workers and brought in bombs, mines, rocket launchers and other weapons disguised as building material.

"The bandits snuck in a large amount of arms, munitions, missiles and explosives hidden by planks, cement and other construction material. This was enough for them to make an extended defense of the building," the source said

They then stashed the weapons away in a case in the basement under the new gym floor before it was laid down, Russian news reports quoted security officials as saying.

A total of 322 people -- including 155 children -- were reported killed, according to the latest toll.

The number of dead was the highest in any single hostage-taking in the history of Russia, which has gone through a decade of warfare in separatist Chechnya.

In May the pro-Kremlin president of Chechnya, Akhmad Kadyrov, was killed in an explosion in a stadium in the Chechen capital, Grozny. The bomb had been hidden in a block of concrete in the stadium, which had just been completed.

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